OFFSET
0,2
COMMENTS
a(n)-(1-(-1)^n) is the inverse binomial transform of the central trinomial coefficients A002426. - N-E. Fahssi, Jan 11 2008
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..1000
FORMULA
E.g.f. 2sinh(x) + BesselI_0(2x)
G.f.: (2x)/(1 - x^2) + 1/Sqrt[1 - 4 x^2]. - N-E. Fahssi, Jan 11 2008
If n is even, a(n) ~ 2^(n+1/2) / sqrt(Pi*n). - Vaclav Kotesovec, Feb 12 2014
MATHEMATICA
CoefficientList[Series[2*Sinh[x] + BesselI[0, 2*x], {x, 0, 20}], x]*Range[0, 20]! (* Vaclav Kotesovec, Feb 12 2014 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Mar 28 2003
STATUS
approved