A133140 a(0) = 2, a(n) = 2^n + 2 for n>=1.

2, 4, 6, 10, 18, 34, 66, 130, 258, 514, 1026, 2050, 4098, 8194, 16386, 32770, 65538, 131074, 262146, 524290, 1048578, 2097154, 4194306, 8388610, 16777218, 33554434, 67108866, 134217730, 268435458, 536870914, 1073741826, 2147483650, 4294967298

Offset: 0

Author

Paul Curtz, Sep 21 2007

Keywords

• nonn
• easy

Comments

Sum of the coefficients of the polynomial Q(n,x)=(1+x)[(1+x)^(n-1)+x^(n-1)], Q(0,x)=2.

Also row sums of A133138. - R. J. Mathar, Jun 12 2008

Links

• Index entries for linear recurrences with constant coefficients, signature (3, -2).

Programs

Mathematica

Table[If[n < 2, 2, 1] + Total[Table[Coefficient[Expand[(1 + x) ((1 + x)^(n - 1) + x^(n - 1))], x^m], {m, 1, n}]], {n, 0, 22}] (* Mats Granvik, May 19 2012 *)
Join[{2},2^Range[40]+2] (* Harvey P. Dale, Aug 16 2014 *)

Formula

a(n)=2*A094373(n). a(n)=A052548(n), n>0. - R. J. Mathar, Jun 12 2008

Extensions

Edited by R. J. Mathar, Jun 12 2008