A277353 - OEIS

%I #7 Oct 10 2016 06:21:15

%S 1,4,52,1456,71344,5422144,591013696,87470027008,16881715212544,

%T 4119138511860736,1239860692070081536,451309291913509679104,

%U 195416923398549691052032,99271797086463243054432256,58471088483926850159060598784,39526455815134550707524964777984

%N a(n) = Product_{k=1..n} (3*k^2+1).

%F a(n) ~ 2*3^(n+1/2) * n^(2*n+1) * sinh(Pi/sqrt(3)) / exp(2*n).

%t Table[Product[3*k^2+1, {k, 1, n}], {n, 0, 15}]

%Y Cf. A101686, A277352, A277354.

%K nonn

%O 0,2

%A _Vaclav Kotesovec_, Oct 10 2016