A105251 a(n) = binomial(n+4,n)*binomial(n+8,n).

1, 45, 675, 5775, 34650, 162162, 630630, 2123550, 6370650, 17381650, 43801758, 103169430, 229265400, 484306200, 978496200, 1900457064, 3563356995, 6473226375, 11428041625, 19658764125, 33026723730, 54295634250, 87501228750, 138447123750, 215362192500

Offset

0,2

Links

T. D. Noe, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (13,-78,286,-715,1287,-1716,1716,-1287,715,-286,78,-13,1).

Formula

G.f.: -(70*x^4+224*x^3+168*x^2+32*x+1)/(x-1)^13. - Colin Barker, Jan 21 2013

From Amiram Eldar, Sep 01 2022: (Start)

Sum_{n>=0} 1/a(n) = 640*Pi^2 - 13925728/2205.

Sum_{n>=0} (-1)^n/a(n) = 640*Pi^2/3 - 90112*log(2)/105 + 471984/1225. (End)

Example

a(0): C(0+4,0)*C(0+8,0) = C(4,0)*C(8,0) = 1*1 = 1;
a(10): C(10+4,10)*C(10+8,10) = C(14,10)*(18,10) = 1001*43758 = 43801758.

Mathematica

f[n_] := Binomial[n + 4, n]Binomial[n + 8, n]; Table[ f[n], {n, 0, 22}] (* Robert G. Wilson v, Apr 20 2005 *)

Prog

(Magma) [Binomial(n+4, n)*Binomial(n+8, n): n in [0..30]]; // Vincenzo Librandi, Jul 31 2015

Crossrefs

Sequence in context: A160234 A110691 A296540 * A099632 A264138 A293971

Adjacent sequences: A105248 A105249 A105250 * A105252 A105253 A105254

Keyword

easy,nonn

Author

Zerinvary Lajos, Apr 14 2005

Extensions

More terms from Robert G. Wilson v, Apr 20 2005

Status

approved