A330516 Expansion of e.g.f. Product_{k>=1} sec(x^k) (even powers only).

1, 1, 17, 601, 44225, 4589041, 781157585, 162882093193, 48519650017025, 17223202538504161, 7898449818361655825, 4193448664548573675961, 2779065418077990268214465, 2061320859693223620523895761, 1836094285018667246330440863185

Offset: 0

Author

Ilya Gutkovskiy, Dec 17 2019

Keywords

• nonn

Crossrefs

Cf. A000364, A203716, A229263, A270294, A270662, A270663, A270664, A270665, A270666, A330514, A330515, A330517.

Programs

Mathematica

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