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**John E. Franklin****Member**- Registered: 2005-08-29
- Posts: 3,564

351

a triangle with 26 rows, pair them up for 13 pairs of 27.

270 + 81 = 351, yup.

**igloo** **myrtilles** **fourmis**

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 90,494

378

Is the sum of two other traingular numbers.

378 = Triangular(12) + Triangular(24)

**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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**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,528

I see what youre up to here.

Everyone is holding off from posting because you all want to hit post #31.

So Im going to have it this way.

The North Circular Road around inner London = 406

Bob

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

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**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,528

Then

(root(4) x 10 + (4 + 5)) x 3 x 5 = 435

Bob

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

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**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,528

Triangular 45 with a triangular 6 between = 465

Bob

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

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**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,528

496 Arrrrhh! Thats perfect!

Bob

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 90,494

528

2^9 + 2^4 = 528

**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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**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,657

561

if HCF(561,b)=1 then b^560 is congruent to 1 modulo 561

*Last edited by anonimnystefy (2011-08-14 22:39:57)*

Here lies the reader who will never open this book. He is forever dead.

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 90,494

595

**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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**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,657

630=2*3*3*5*7=97+101+103+107+109+113 which are consecutive primes

Here lies the reader who will never open this book. He is forever dead.

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 90,494

666

The mark of the beast.

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

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**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,657

703-a Kaprekar number

*Last edited by anonimnystefy (2011-05-25 22:22:06)*

Here lies the reader who will never open this book. He is forever dead.

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

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**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,657

740-a non-totient number

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 90,494

Hi;

741 a triangular number.

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

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**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,657

oh yes you are right

catching up:

780-also a hexagonal number,Harshad number,sum of ten consecutive primes:

780=59 + 61 + 67 + 71 + 73 + 79 + 83 + 89 + 97 + 101

820-Harshad number:

8+2+0|820

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**John E. Franklin****Member**- Registered: 2005-08-29
- Posts: 3,564

861 = 41 + 820

41 by 21 = 800 + 1 + 40 + 20

**igloo** **myrtilles** **fourmis**

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 90,494

Hi;

903 not a prime.

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

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**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,657

946-not a prime either.

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 90,494

990 almost a prime.

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

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**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,657

1035-first triangular number greater than 1000.

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 90,494

1081 also not a prime.

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

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**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,657

1128-not not a not-prime

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 90,494

1176 add 600 and it has meaning today!

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

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**mathaholic****Member**- From: Juliania
- Registered: 2012-11-29
- Posts: 2,893
- Website

"What is the square root of 2? 1.4141592653589793238" Seriously, I thought it was that. Too round?

3.141592653589793238...

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 90,494

The next triangular number is 1275.

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

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