A369389 a(n) is the constant term in expansion of Product_{k=1..n} (x^(k^2) + 1 + 1/x^(k^2))^2.

1, 3, 9, 35, 141, 745, 3955, 23985, 155527, 1060941, 7393765, 53041015, 387815175, 2882682967, 21715452927, 165583974835, 1275674593889, 9918184576835, 77738274996385, 613753581566079, 4877383708962749, 38989308129231703, 313354624116918229, 2530796548734844153

Offset: 0

Author

Ilya Gutkovskiy, Jan 22 2024

Keywords

• nonn

Crossrefs

Cf. A047653, A156181, A350249, A350495.

Programs

Mathematica

Table[Coefficient[Product[(x^(k^2) + 1 + 1/x^(k^2))^2, {k, 1, n}], x, 0], {n, 0, 23}]