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

%I #10 May 05 2022 21:03:00

%S 1,24,420,6720,102960,1537536,22573824,327444480,4707014400,

%T 67190323200,953748956160,13476348887040,189694258790400,

%U 2661556369489920,37240665709608960,519828326870679552,7240915141833719808,100675825501431398400,1397476339698440601600

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

%H Amiram Eldar, <a href="/A072975/b072975.txt">Table of n, a(n) for n = 0..883</a>

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

%t Table[2^n * Binomial[3*n, n] * (3*n + 1), {n, 0, 20}] (* _Amiram Eldar_, May 04 2022 *)

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

%K easy,nonn

%O 0,2

%A _Benoit Cloitre_, Aug 13 2002

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Last modified September 27 00:17 EDT 2023. Contains 365669 sequences. (Running on oeis4.)