OFFSET
0,4
COMMENTS
Lah transform of the sequence 1, 0, 1, 0, 5, 0, 61, 0, 1385, ... (A000364 interspersed with zeros).
LINKS
N. J. A. Sloane, Transforms
FORMULA
E.g.f.: sec(x/(1 - x)).
a(n) ~ 4 * n! * (Pi+2)^(n-1) / Pi^(n+1). - Vaclav Kotesovec, Jul 28 2018
MAPLE
a:=series(sec(x/(1 - x)), x=0, 23): seq(n!*coeff(a, x, n), n=0..22); # Paolo P. Lava, Mar 26 2019
MATHEMATICA
nmax = 22; CoefficientList[Series[Sec[x/(1 - x)], {x, 0, nmax}], x] Range[0, nmax]!
Table[Sum[Binomial[n - 1, k - 1] Abs[EulerE[k]] n!/k!, {k, 0, n}], {n, 0, 22}]
PROG
(PARI) x = 'x + O('x^30); Vec(serlaplace(1/cos(x/(1 - x)))) \\ Michel Marcus, Jul 28 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Jul 27 2018
STATUS
approved