9,73,241,561,1081,1849,_?_ • Hacker News Board

Re: 9,73,241,561,1081,1849,_?_

#21

Post by jriddycuz » Thu, Nov 05, 2009, 6:07 PM UTC

graywh wrote: post #13

Was surprised to see this happen: http://www.wolframalpha.com/input/?i=0%2C1%2C2%2C4%2C8%2C16%...

Agreed, don't start with zero for that. There's no real number n such that 2^n = 0, so the the closed-form expression you were seeking won't be found that way.

Re: 9,73,241,561,1081,1849,_?_

#22

Post by bdr » Thu, Nov 05, 2009, 6:08 PM UTC

amichail wrote: post #15

bdr wrote: post #14

Earlier quoted context omitted.

Here's one interpretation: What will the simplest program that outputs these numbers output next?

How will you prove that your answer is correct?

Well, that could be done by brute force. Realistically, though, it's more about whether anyone can beat your answer.

Re: 9,73,241,561,1081,1849,_?_

#23

Post by jriddycuz » Thu, Nov 05, 2009, 6:10 PM UTC

seven wrote: post #20

nixme wrote: post #18

Earlier quoted context omitted.

Works properly if you take out the 0 term: http://www.wolframalpha.com/input/?i=1,2,4,8,16,32,64,128,25...

This works with 0: http://www.wolframalpha.com/input/?i=0,1,2,4,8,16,32,64,128,...

Yes but in the recurrence relation, it said "for all n >= 1". I guess the additional term was the tipping point that let mathematica infer that the meat of the sequence was for n >= 1.

Re: 9,73,241,561,1081,1849,_?_

#24

Post by moron4hire » Thu, Nov 05, 2009, 6:11 PM UTC

Not to be too harsh here, but...

I've been using "difference tables" (without calling it that) since I was 10 years old. I don't mean this to be bragging at all, because I didn't think (and still don't think) it was at all remarkable. It's just a basic method of analysis.

Re: 9,73,241,561,1081,1849,_?_

#25

Post by markerdmann » Thu, Nov 05, 2009, 6:16 PM UTC

perone wrote: post #2

http://www.wolframalpha.com/input/?i=9%2C73%2C241%2C561%2C10...

Wolfram Alpha has been a bit of a disappointment in terms of natural language parsing, but it's hard not to be impressed by the way it handles mathematical inputs.

Does anyone know if the natural language parsing is showing improvement, or does it still choke on most inputs?

Re: 9,73,241,561,1081,1849,_?_

#26

Post by niyazpk » Thu, Nov 05, 2009, 6:24 PM UTC

You can see a discussion about difference tables here: http://www.physicsforums.com/showthread.php?t=114995

Re: 9,73,241,561,1081,1849,_?_

#27

Post by [deleted] » Thu, Nov 05, 2009, 6:32 PM UTC

Leon wrote: post #19

amichail wrote: post #15

Earlier quoted context omitted.

How will you prove that your answer is correct?

occam's razor

[deleted]

Re: 9,73,241,561,1081,1849,_?_

#28

Post by duh » Thu, Nov 05, 2009, 6:33 PM UTC

amichail wrote: post #15

bdr wrote: post #14

Earlier quoted context omitted.

Here's one interpretation: What will the simplest program that outputs these numbers output next?

How will you prove that your answer is correct?

You can only prove that the answer is incorrect.

Re: 9,73,241,561,1081,1849,_?_

#29

Post by Emore » Thu, Nov 05, 2009, 6:41 PM UTC

moron4hire wrote: post #24

Not to be too harsh here, but... I've been using "difference tables" (without calling it that) since I was 10 years old. I don't mean this to be bragging at all, because I didn't think (and still don't think) it was at all remarkable. It's just a basic method of analysis.

Same here. We learned of them in 4th grade, in Sweden.

Re: 9,73,241,561,1081,1849,_?_

#30

Post by tkahn6 » Thu, Nov 05, 2009, 6:43 PM UTC

Can anyone explain why it takes so long to find the equation differentially? I understand that is subjective, but the 'constants' are only constant from y''' to y''. From y'' to y' the 'constant' is linear (meaning you have to solve for change in y' - y) and the 'constant' is quadratic from y' to y.

Basically you can't just integrate each DE and solve for a constant C by finding the value of the lower order DE where x=1 and finding the difference. Why not?

I'm in Calc BC in high school so this could be a stupid question.