A350306 - OEIS

A350306

a(n) is the constant term in the expansion of Product_{k=1..n} (x^k + 1 + 1/x^k)^k.

%I #11 Dec 24 2021 11:04:24

%S 1,1,3,57,2855,459597,240485241,395649695145,2023017357650345,

%T 31899582278283495743,1542718311570632349138107,

%U 227912729019868361872929934159,102547791095886594007005283976727239,140202209701199998336689204011032887220183

%N a(n) is the constant term in the expansion of Product_{k=1..n} (x^k + 1 + 1/x^k)^k.

%t a[n_] := Coefficient[Series[Product[(x^k + 1 + 1/x^k)^k, {k, 1, n}], {x, 0, 0}], x, 0]; Array[a, 14, 0] (* _Amiram Eldar_, Dec 24 2021 *)

%o (PARI) a(n) = polcoef(prod(k=1, n, (x^k+1+1/x^k)^k), 0);

%Y Cf. A350283, A350305, A350308.

%K nonn

%O 0,3

%A _Seiichi Manyama_, Dec 23 2021