OFFSET
0,6
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..200
J. Cigler, Some remarks about q-Chebyshev polynomials and q-Catalan numbers and related results, arXiv:1312.2767 [math.CO], 2013.
FORMULA
a(n) ~ n! * sqrt(2) * cos(1-(3*n-1)*(Pi/4)) / (2^(n/2) * exp(1)). - Vaclav Kotesovec, Jan 24 2015
MATHEMATICA
With[{nn=30}, CoefficientList[Series[Exp[x]/Cosh[Log[1+x]], {x, 0, nn}], x] Range[0, nn]!] (* Harvey P. Dale, Aug 27 2013 *)
CoefficientList[Series[(2*E^x*(1 + x))/(1 + (1 + x)^2), {x, 0, 20}], x] * Range[0, 20]! (* Vaclav Kotesovec, Jan 24 2015 *)
CROSSREFS
KEYWORD
sign,easy
AUTHOR
EXTENSIONS
Extended with signs by Olivier Gérard, Mar 15 1997
Definition clarified and prior Mathematica program replaced by Harvey P. Dale, Aug 27 2013
STATUS
approved