A353610 Product_{n>=1} (1 + a(n)*x^(2*n)/(2*n)!) = sec(x).

1, 5, -14, 1777, -14744, 247994, -74928944, 42293543177, -1163849271296, 95795966018440, -44942000161435904, 4494117864138588514, -3539995034294896016384, 770158600620174924566672, -510461123036204706738612224, 1162153458061287151457003978297

Offset

1,2

Links

Table of n, a(n) for n=1..16.

Mathematica

nn = 16; f[x_] := Product[(1 + a[n] x^(2 n)/(2 n)!), {n, 1, nn}]; sol = SolveAlways[0 == Series[f[x] - Sec[x], {x, 0, 2 nn}], x]; Table[a[n], {n, 1, nn}] /. sol // Flatten

Crossrefs

Cf. A000364, A006973, A137852, A353607, A353608, A353609, A353611.

Sequence in context: A128946 A156219 A000331 * A306155 A082269 A367030

Adjacent sequences: A353607 A353608 A353609 * A353611 A353612 A353613

Keyword

sign

Author

Ilya Gutkovskiy, May 07 2022

Status

approved