Find the next number.

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Find the next number.

7, 4, 10, 26, 53, 92, 144,____

jjane

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Re: Find the next number.

Sorry, OEIS says that those numbers don't exist in that order.
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Puck

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Re: Find the next number.

Puck wrote:Sorry, OEIS says that those numbers don't exist in that order.

Then the whole point is to try and find that order that they belong in.

Let's see, 7, 4, 10...

Might it be some quadratic function?

There's also:

Spoiler:
7 + 4 - 1 = 10
4 + 10 + 12 = 26
26 + 26 + 1 = 53
26 + 53 + 23 = 92
53 + 92 - 1 = 144

So maybe 92 + 144 + 34 is the next term, or 270.
Last edited by tricky77puzzle on Fri Oct 17, 2008 11:05 pm UTC, edited 1 time in total.
tricky77puzzle
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Re: Find the next number.

I know what the next number is. I obtained my answer using finite differences.

Is this a homework problem?
++\$_
Mo' Money

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Re: Find the next number.

Show our workings? You're making us do your homework? Tsk Tsk!
Ratio

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Re: Find the next number.

tricky77puzzle wrote:4 + 10 + 10 = 26

O RLY?
Lycur

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Re: Find the next number.

Lycur wrote:
tricky77puzzle wrote:4 + 10 + 10 = 26

O RLY?

okay, damn. I, uh... mae a miscalculation.
tricky77puzzle
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Re: Find the next number.

Spoiler:
The answer is 210. Take differences between terms.

thc

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Re: Find the next number.

thc wrote:
Spoiler:
The answer is 210. Take differences between terms.

Uh huh. That's a very big spoiler. Thanks a lot... so It was a quadratic function!
tricky77puzzle
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Re: Find the next number.

tricky77puzzle wrote:
thc wrote:
Spoiler:
The answer is 210. Take differences between terms.

Uh huh. That's a very big spoiler. Thanks a lot... so It was a quadratic function!

Spoiler:
Looks more like a cubic to me, but that's the answer I got as well.
++\$_
Mo' Money

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Re: Find the next number.

++\$_ wrote:
tricky77puzzle wrote:
thc wrote:
Spoiler:
The answer is 210. Take differences between terms.

Uh huh. That's a very big spoiler. Thanks a lot... so It was a quadratic function!

Spoiler:
Looks more like a cubic to me, but that's the answer I got as well.

If it were cubic, it wouldn't go down, then up, unless it were a cubic plus some linear term.

The reason it's... oh, wait, yes, it is a cubic. I am dumb...
tricky77puzzle
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Re: Find the next number.

I don't get it. Care to explain?
fransisco4

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Re: Find the next number.

fransisco4 wrote:I don't get it. Care to explain?

Spoiler:
Take the difference between each consecutive number in the sequence. You get -3, 6, 16, 27, 39, 52. Now do it again with that sequence to get 9, 10, 11, 12, 13. The pattern there should be rather obvious. 52+14 = 66, so the next term in the original sequence is 144+66 = 210.
douglasm

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Re: Find the next number.

It really could be anything. There's no way to know what formula we're talking about from finitely many terms. The cubic one may seem simpler, but that doesn't make it any more correct.

the right answer is, of course, 42
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qinwamascot

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Re: Find the next number.

qinwamascot wrote:It really could be anything. There's no way to know what formula we're talking about from finitely many terms. The cubic one may seem simpler, but that doesn't make it any more correct.

the right answer is, of course, 42

Really, it could be anything.

I could define f(x) as the function that returns:

f(x|x<1) = f(x + 1) - 2(f(x + 2))
f(1) = 7
f(2) = 4
f(3) = 10
f(4) = 26
f(5) = 53
f(6) = 92
f(7) = 144
f(8) = 42
f(x|x>8) = 42
tricky77puzzle
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Re: Find the next number.

I'm pretty sure this discussion was already held
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Office_Shredder

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Re: Find the next number.

Office_Shredder wrote:I'm pretty sure this discussion was already held

Yeah. It was in maths. Gotta say I side with Token on this one.

Token wrote:
Frimble wrote:It irritates me that this sort of question frequently appears on 11+ tests and GCSE Maths exams. The next term could be any number at all, yet only one specific number is marked as correct.

It irritates ME that people think "it could be anything" is a clever answer.
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jestingrabbit

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Re: Find the next number.

for the record, it wasn't my homework. i'm not even in school right now.

(it was my MOM's homework)

thanks, dudes.

jjane

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Location: sacramento, ca

Re: Find the next number.

{7, 4, 10, 26, 53, 92, 144, 210, 291, 388, 502, 634, 785, 956, 1148, 1362, 1599, 1860, 2146, 2458, 2797, 3164, 3560, 3986, 4443, 4932, 5454, 6010, 6601, 7228, 7892, 8594}

a(n)=1/6*(108 - 88*n + 21*n^2 + n^3)
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