A072975 a(n) = 2^n*binomial(3*n,n)*(3*n+1).

1, 24, 420, 6720, 102960, 1537536, 22573824, 327444480, 4707014400, 67190323200, 953748956160, 13476348887040, 189694258790400, 2661556369489920, 37240665709608960, 519828326870679552, 7240915141833719808, 100675825501431398400, 1397476339698440601600

Offset

0,2

Links

Amiram Eldar, Table of n, a(n) for n = 0..883

Formula

Sum_{k>=0} 1/a(k) = ( Pi+3*log(2) )/5 = 1.04420683905392583334286...

Mathematica

Table[2^n * Binomial[3*n, n] * (3*n + 1), {n, 0, 20}] (* Amiram Eldar, May 04 2022 *)

Prog

(PARI) a(n)=2^n*binomial(3*n, n)*(3*n+1)

Crossrefs

Sequence in context: A267166 A016326 A287994 * A062193 A016268 A175199

Adjacent sequences: A072972 A072973 A072974 * A072976 A072977 A072978

Keyword

easy,nonn

Author

Benoit Cloitre, Aug 13 2002

Status

approved