Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ π -¹ ² ³ °

You are not logged in.

- Topics: Active | Unanswered

Pages: **1**

**pal2006****Guest**

2,3,10,39,172,?

what will be the next no.?and how?

**luca-deltodesco****Member**- Registered: 2006-05-05
- Posts: 1,470

pal2006 wrote:

2,3,10,39,172,?

what will be the next no.?and how?

ive tried loads of things, but im stumped

The Beginning Of All Things To End.

The End Of All Things To Come.

Offline

**Ricky****Moderator**- Registered: 2005-12-04
- Posts: 3,791

And so is the online encyclopedia of integer sequences. Where is this sequence coming from? A math textbook? A teacher? You just put a bunch of numbers next to each other?

"In the real world, this would be a problem. But in mathematics, we can just define a place where this problem doesn't exist. So we'll go ahead and do that now..."

Offline

**pal2006****Guest**

This Question Is From One Of The Question Banks Of M.b.a

**MathsIsFun****Administrator**- Registered: 2005-01-21
- Posts: 7,559

Maybe not an integer sequence ... could be real numbers and the sequence is exponential.

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

Offline

**Ricky****Moderator**- Registered: 2005-12-04
- Posts: 3,791

Huh? All of the numbers given are integers. Are you suggesting the numbers on down the line can be decimals?

"In the real world, this would be a problem. But in mathematics, we can just define a place where this problem doesn't exist. So we'll go ahead and do that now..."

Offline

**jukka****Guest**

The answer is veeeeery logical and in my opinion very simple... You just have to see those numbers in a different way,

If u still havent found what u are looking for:

SPOILER!!!

Try to add two of numbers with eachother...

**numen****Member**- Registered: 2006-05-03
- Posts: 115

jukka, I thought I had it too. But it doesn't work with the last number 172, I get it to something else am I missing something?

**Edit:** Nevermind, I got it now

*Last edited by numen (2006-06-18 03:00:45)*

Bang postponed. Not big enough. Reboot.

Offline

**luca-deltodesco****Member**- Registered: 2006-05-05
- Posts: 1,470

numen wrote:

jukka, I thought I had it too. But it doesn't work with the last number 172, I get it to something else am I missing something?

Edit:Nevermind, I got it now

well i dunno about the nevermind, but when i first posted, i thought i had got it with adding the numbers via

u[n] = (n-1)(u[n-1]+u[n-2])

i.e

u[3] = 2*(2+3) = 10

u[4] = 3*(10+3) = 39

u[5] = 4*(39+10) = 186 =/= 172, and then i realised it was wrong

so what is the answer

The Beginning Of All Things To End.

The End Of All Things To Come.

Offline

**numen****Member**- Registered: 2006-05-03
- Posts: 115

Bang postponed. Not big enough. Reboot.

Offline

Pages: **1**