cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A349468 a(n) = (4*n)! / (n! * (2*n)!).

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%I A349468 #11 Mar 06 2022 08:31:12
%S A349468 1,12,840,110880,21621600,5587021440,1799020903680,693908062848000,
%T A349468 311911674250176000,160114659448423680000,92418181433630148096000,
%U A349468 59248455951814527670272000,41770161446029242007541760000,32118041062654484854414417920000,26749739913610806671605150924800000
%N A349468 a(n) = (4*n)! / (n! * (2*n)!).
%F A349468 E.g.f.: 2 * EllipticK( 16*sqrt(x) / (1 + 8*sqrt(x)) ) / (Pi * sqrt(1 + 8*sqrt(x))).
%F A349468 a(n) is the coefficient of x^n in expansion of d^n/dx^n g(x), where g(x) is the g.f. of central binomial coefficients (A000984).
%F A349468 a(n) = n! * A000897(n) = A009120(n) / n! = A166338(n) / (2*n)! = A001448(n) * A001813(n).
%F A349468 a(n) ~ 64^n * n^(n-1/2) / (sqrt(Pi) * exp(n)).
%F A349468 D-finite with recurrence n*a(n) -4*(4*n-1)*(4*n-3)*a(n-1)=0. - _R. J. Mathar_, Mar 06 2022
%t A349468 Table[(4 n)!/(n! (2 n)!), {n, 0, 14}]
%t A349468 nmax = 14; CoefficientList[Series[2 EllipticK[16 Sqrt[x]/(1 + 8 Sqrt[x])]/(Pi Sqrt[1 + 8 Sqrt[x]]), {x, 0, nmax}], x] Range[0, nmax]!
%t A349468 Table[SeriesCoefficient[D[1/Sqrt[1 - 4 x], {x, n}], {x, 0, n}], {n, 0, 14}]
%o A349468 (PARI) a(n) = (4*n)! / (n! * (2*n)!) \\ _Andrew Howroyd_, Nov 20 2021
%Y A349468 Cf. A000897, A000984, A001448, A001813, A009120, A166338.
%K A349468 nonn,easy
%O A349468 0,2
%A A349468 _Ilya Gutkovskiy_, Nov 18 2021