A369387 a(n) is the constant term in expansion of Product_{k=1..n} (x^(2*k-1) + 1 + 1/x^(2*k-1))^2.

1, 3, 9, 43, 243, 1539, 10557, 75595, 558117, 4218077, 32466849, 253624579, 2005655781, 16024596491, 129159081787, 1048931938309, 8574963650419, 70507361919587, 582730070295737, 4838280518142269, 40336851095845719, 337541054046113077, 2834101218805540871

Offset

0,2

Links

Table of n, a(n) for n=0..22.

Mathematica

Table[Coefficient[Product[(x^(2 k - 1) + 1 + 1/x^(2 k - 1))^2, {k, 1, n}], x, 0], {n, 0, 22}]

Crossrefs

Cf. A047653, A156181, A369343.

Sequence in context: A275781 A199140 A154606 * A232216 A167143 A136732

Adjacent sequences: A369384 A369385 A369386 * A369388 A369389 A369390

Keyword

nonn

Author

Ilya Gutkovskiy, Jan 22 2024

Status

approved