A101480 E.g.f. (1/cosh(x)+tanh(x))*(exp(2*x)-exp(-x))/3.

0, 1, 3, 3, 3, 11, 63, 43, -837, 171, 34023, 683, -1800477, 2731, 132912783, 10923, -12927652917, 43691, 1603253204343, 174763, -246914125142157, 699051, 46232582930156703, 2796203, -10343022775699132197, 11184811, 2724715006195438297863, 44739243, -834839760935753154167037

Offset: 0

Author

Paul Barry, Jan 21 2005

Keywords

• easy
• sign

Comments

A transform of the Jacobsthal numbers.

a(2n)=A007583(n)=(2*4^n+1)/3.

Crossrefs

Cf. A101473, A001045.

Programs

Mathematica

With[{nn=30},CoefficientList[Series[(1/Cosh[x]+Tanh[x]) (Exp[2x]- Exp[-x])/3, {x,0,nn}],x]Range[0,nn]!] (* Harvey P. Dale, Aug 22 2012 *)

Extensions

Corrected by N. J. A. Sloane, Nov 05 2005