A327994 a(n) is the constant term in the expansion of (1 + (1+x)*(1+y) + (1+1/x)*(1+1/y) + (1+1/x^2)*(1+1/y^2))^n.

1, 4, 22, 157, 1342, 12694, 126601, 1301353, 13647622, 145280776, 1564974682, 17022150688, 186647326849, 2060538384454, 22880172406939, 255336518921572, 2861956399934038, 32201882791307904, 363561893114484868, 4117138703073839926, 46751784944876067562

Offset

0,2

Links

Table of n, a(n) for n=0..20.

Mathematica

F[n_] := Expand[(1+(1+x)(1+y) + (1+1/x)(1+1/y) + (1+1/x^2)(1+1/y^2))^n];
a[n_] := SeriesCoefficient[F[n], {x, 0, 0}, {y, 0, 0}]; a /@ Range[0, 20]

Crossrefs

Cf. A002893.

Sequence in context: A198053 A197925 A112697 * A113717 A124563 A122704

Adjacent sequences: A327991 A327992 A327993 * A327995 A327996 A327997

Keyword

nonn

Author

Peter Luschny, Oct 28 2019

Status

approved