A369372 a(n) is the constant term in expansion of Product_{k=1..n} (x^k + 1 + 1/x^k)^3.

1, 7, 85, 1437, 26707, 534513, 11255951, 245612031, 5503639327, 125900330437, 2928092906281, 69026845135479, 1645689594867257, 39611576627651927, 961279033420170871, 23494000801494204647, 577777092945262623161, 14287061769367391787065, 355010279665452190629001

Offset

0,2

Links

Table of n, a(n) for n=0..18.

Mathematica

Table[Coefficient[Product[(x^k + 1 + 1/x^k)^3, {k, 1, n}], x, 0], {n, 0, 18}]

Prog

(PARI) a(n) = polcoef(prod(k=1, n, (x^k + 1 + 1/x^k)^3), 0); \\ Michel Marcus, Jan 22 2024

Crossrefs

Cf. A007576, A124995, A156181, A369373.

Sequence in context: A216698 A317353 A302565 * A049412 A346984 A361065

Adjacent sequences: A369369 A369370 A369371 * A369373 A369374 A369375

Keyword

nonn

Author

Ilya Gutkovskiy, Jan 21 2024

Status

approved