A330517 Expansion of e.g.f. Product_{k>=1} sech(x^k) (even powers only).

1, -1, -7, -241, -4495, -652801, -15004375, -7047990769, 1597056262625, -360304327144321, 286464442762907225, 560117092794518159, 78257061390674957994065, 5684812583023438995911039, 45666128878264725133259682185

Offset

0,3

Links

Table of n, a(n) for n=0..14.

Mathematica

nmax = 14; Table[(CoefficientList[Series[Product[Sech[x^k], {k, 1, nmax}], {x, 0, 2 nmax}], x] Range[0, 2 nmax]!)[[n]], {n, 1, 2 nmax + 1, 2}]

Crossrefs

Cf. A000364, A203716, A229263, A270294, A270662, A270663, A270664, A270665, A270666, A330514, A330515, A330516.

Sequence in context: A251594 A210248 A200961 * A086214 A133589 A296377

Adjacent sequences: A330514 A330515 A330516 * A330518 A330519 A330520

Keyword

sign

Author

Ilya Gutkovskiy, Dec 17 2019

Status

approved