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## #1 2011-03-01 02:55:32

John E. Franklin
Member
Registered: 2005-08-29
Posts: 3,582

### Let's make triangular numbers.

The first triangular number is 1.
To continue this thread, simply
add 2, then 3, then 4, on forever
to make triangular numbers.

So I'll go first:

1
(one)

igloo myrtilles fourmis

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## #2 2011-03-01 13:28:07

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,758

### Re: Let's make triangular numbers.

3 is triangular and prime.

In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

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## #3 2011-03-02 05:17:16

G-man
Member
Registered: 2011-02-28
Posts: 16

### Re: Let's make triangular numbers.

6  Its triangular & first composite which isn't a square.

Maths!......

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## #4 2011-03-02 09:41:30

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,758

### Re: Let's make triangular numbers.

10 - The number of balls in a 10 ball rack. The first 2 digit triangular number! Also it is larger than 1 - 9 and has a zero in it.

In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

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## #5 2011-03-02 12:31:13

John E. Franklin
Member
Registered: 2005-08-29
Posts: 3,582

### Re: Let's make triangular numbers.

15
5 x (6/2)

igloo myrtilles fourmis

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## #6 2011-03-02 15:17:51

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,758

### Re: Let's make triangular numbers.

21 everybody's favorite number

In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

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## #7 2011-03-02 15:43:46

MathsIsFun
Registered: 2005-01-21
Posts: 7,555

### Re: Let's make triangular numbers.

28: has factors 1, 2, 4, 7, 14, 28 and reminds me of February

"The physicists defer only to mathematicians, and the mathematicians defer only to God ..."  - Leon M. Lederman

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## #8 2011-03-02 15:53:48

G-man
Member
Registered: 2011-02-28
Posts: 16

### Re: Let's make triangular numbers.

36
square of product of first two consecutive primes.

Maths!......

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## #9 2011-03-02 21:13:39

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,758

### Re: Let's make triangular numbers.

45 - ( Colt ) the best automatic ever made.

In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

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## #10 2011-03-03 15:53:14

G-man
Member
Registered: 2011-02-28
Posts: 16

55..........

Maths!......

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## #11 2011-03-03 18:17:35

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,758

### Re: Let's make triangular numbers.

66 - the 11 the triangular number and the name of a now infamous highway here in the southwest.

In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

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## #12 2011-03-06 02:21:55

matthen
Member
Registered: 2011-03-06
Posts: 8

### Re: Let's make triangular numbers.

78

note these triangular numbers go:
...,45,55,66,78,91, quite cool that 4,5,6,7,8,9 appear in order with no interruptions!

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## #13 2011-03-06 05:49:43

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,758

### Re: Let's make triangular numbers.

91 The most powerful triangular number and the one that wants to be a square the most. Also it is the only one that is 7 * 13.

In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

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## #14 2011-03-22 11:31:19

John E. Franklin
Member
Registered: 2005-08-29
Posts: 3,582

### Re: Let's make triangular numbers.

105=14+91
(14/2)*15

igloo myrtilles fourmis

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## #15 2011-03-22 12:48:39

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,758

### Re: Let's make triangular numbers.

The 15th triangular number is 120. Which is also 5!.

In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

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## #16 2011-03-22 13:58:55

G-man
Member
Registered: 2011-02-28
Posts: 16

### Re: Let's make triangular numbers.

136.........1, 3 & 6 are first 3 triangle numbers.

Maths!......

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## #17 2011-03-22 14:28:21

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,758

### Re: Let's make triangular numbers.

153

Is a square away from 2 squares. 12^2 + 3^3 = 153 and 13^2 - 4^2 = 153

In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

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## #18 2011-04-05 02:21:55

John E. Franklin
Member
Registered: 2005-08-29
Posts: 3,582

### Re: Let's make triangular numbers.

171
153 + 18 = 171
(19 x 18) / 2

igloo myrtilles fourmis

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## #19 2011-04-05 02:50:56

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,758

### Re: Let's make triangular numbers.

190

The famous 190 Bowery St.

http://nymag.com/realestate/vu/2008/09/50481/

In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

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## #20 2011-04-16 08:29:10

John E. Franklin
Member
Registered: 2005-08-29
Posts: 3,582

### Re: Let's make triangular numbers.

210
210 = 190 + 20
210 = 14 x 15 = (21 x 20) / 2 on this post # 20.

igloo myrtilles fourmis

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## #21 2011-04-16 08:51:43

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,758

### Re: Let's make triangular numbers.

231

One of the permutations of 123.

In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

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## #22 2011-04-16 11:34:54

John E. Franklin
Member
Registered: 2005-08-29
Posts: 3,582

### Re: Let's make triangular numbers.

253
253 = 231 + 22 = (1 + 22)+(2 + 21)+...(9 + 14)+(10 + 13)+(11 + 12)
= 11 x 23 = (23 x 22) / 2
This triangular number can form a digital triangle with 22 rows in 3 angles differing by 120 degrees.

igloo myrtilles fourmis

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## #23 2011-04-16 14:40:42

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,758

### Re: Let's make triangular numbers.

276

And that is real close to 253.

In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

Offline

## #24 2011-04-17 12:13:04

John E. Franklin
Member
Registered: 2005-08-29
Posts: 3,582

### Re: Let's make triangular numbers.

300

Yeah 300!!!!   276 + 24.    (25 x 24) / 2       A triangle with 24 rows.

igloo myrtilles fourmis

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## #25 2011-04-17 12:20:22

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,758

### Re: Let's make triangular numbers.

325 which is 3*5 - 2 = 13.

In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

Offline