A139814 a(n)=a(n-1)+a(n-2)+a(n-3)+2a(n-4); a(0)=0,a(1)=1,a(2)=3,a(3)=7.

0, 1, 3, 7, 11, 23, 47, 95, 187, 375, 751, 1503, 3003, 6007, 12015, 24031, 48059, 96119, 192239, 384479, 768955, 1537911, 3075823, 6151647, 12303291, 24606583, 49213167, 98426335, 196852667, 393705335, 787410671, 1574821343, 3149642683

Offset: 0

Author

Paul Curtz, May 23 2008

Keywords

• nonn
• easy

Links

• Index entries for linear recurrences with constant coefficients, signature (1,1,1,2).

Crossrefs

Cf. A132429.

Programs

Mathematica

LinearRecurrence[{1,1,1,2},{0,1,3,7},35]  (* Harvey P. Dale, Apr 20 2011 *)

Formula

O.g.f.: -x(1+2x+3x^2)/((2x-1)(1+x)(x^2+1)). a(n) = (-1)^(n+1)/3 +11*2^n/15 -2*(-1)^[n/2]*A000034(n)/5 . - R. J. Mathar, May 24 2008

Extensions

More terms from R. J. Mathar, May 24 2008