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Alternative solution to Series with Catalan numbers in Wolfram|Alpha?

Posted 8 years ago

Dear community-friends from Mathematica

For this problem: http://www.wolframalpha.com/input/?i=SUM+from+k%3D0+to+inf+%28%28CatalanNumber[k]%2F2^%282k%2B1%29%29^2*%2813*k%2B17%29%29 a much simplier solution (than based on Gamma-functions) exists.

Will Mathematica be able to find this solution too? Please note, I offered my support regarding this matter at least five times (without success) via wolframalpha-support.

Best regards

Ralf Steiner

POSTED BY: Ralf Steiner
5 Replies
Posted 8 years ago

Dear David

That above in Mathematica notation works, but not this (similar also in Mathematica notation): Sum[(CatalanNumber[k]/2^(2 k + 1))^2 (17 k + 19), {k, 0, Infinity}]

Input interpretation: sum(k=0)^infinity (Ck/2^(2 k+1))^2 (17 k+19)

Convergence tests: The ratio test is inconclusive.

By the comparison test, the series converges.

Partial sum formula: sum(k=0)^n (Ck/2^(2 k+1))^2 (17 k+19) = (25 n^3 Gamma(1/2 (2 n+3))^2+127 n^2 Gamma(1/2 (2 n+3))^2+208 n Gamma(1/2 (2 n+3))^2-2 pi Gamma(n+3)^2+108 Gamma(1/2 (2 n+3))^2)/(pi Gamma(n+3)^2)

POSTED BY: Ralf Steiner

Dear Ralf

By doing these activities below you can prevent unnatural behavior:

1.Remove the all cache and cookies from your web browser.

2.And try again ,it should work.

POSTED BY: Mariusz Iwaniuk
Posted 8 years ago

Try putting the entire problem in Mathematica notation:

Sum[(CatalanNumber[k]/2^(2 k + 1))^2 (13 k + 17), {k, 0, Infinity}]

POSTED BY: David Kirby
Posted 8 years ago

Dear Mariusz

That is right. But when I (standard user) ask wolframalpha the same like you I get only these results:

Input interpretation: sum(k=0)^infinity (Ck/2^(2 k+1))^2 (13 k+17)

Convergence tests: The ratio test is inconclusive.

By the comparison test, the series converges.

Partial sum formula: sum(k=0)^n (Ck/2^(2 k+1))^2 (13 k+17) = (29 n^3 Gamma(1/2 (2 n+3))^2+149 n^2 Gamma(1/2 (2 n+3))^2+248 n Gamma(1/2 (2 n+3))^2-4 pi Gamma(n+3)^2+132 Gamma(1/2 (2 n+3))^2)/(pi Gamma(n+3)^2)

Partial sums:

More terms
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POSTED BY: Ralf Steiner

Mathematica says:

Sum[(CatalanNumber[k]/2^(2 k + 1))^2 (13 k + 17), {k, 0, Infinity}]
(* 29/Pi-4  *)

enter image description here

POSTED BY: Mariusz Iwaniuk
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