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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. 0
1, 4, 22, 157, 1342, 12694, 126601, 1301353, 13647622, 145280776, 1564974682, 17022150688, 186647326849, 2060538384454, 22880172406939, 255336518921572, 2861956399934038, 32201882791307904, 363561893114484868, 4117138703073839926, 46751784944876067562 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,2
LINKS
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
KEYWORD
nonn
AUTHOR
Peter Luschny, Oct 28 2019
STATUS
approved

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Last modified March 29 11:45 EDT 2024. Contains 371278 sequences. (Running on oeis4.)