A113836 a(n) = Sum[2^(A001651(i-1)-1), {i,1,n}].

1, 3, 11, 27, 91, 219, 731, 1755, 5851, 14043, 46811, 112347, 374491, 898779, 2995931, 7190235, 23967451, 57521883, 191739611, 460175067, 1533916891, 3681400539, 12271335131, 29451204315, 98170681051, 235609634523

Offset: 1

Author

Artur Jasinski, Jan 27 2006

Keywords

• nonn

Comments

From Reinhard Zumkeller, Feb 22 2010: (Start)

For n>1: a(n)=A173593(3*n-5): terms of A173593 ending with digits '11' in binary representation;

for n>0: a(n)=A033129(3*n-1); a(n+1)-a(n)=ABS(A094014(n)). (End)

Examples

			a(2) = 2^(A001651(0)-1) + 2^(A001651(1)-1) = 2^0 + 2^1 = 3
		

Crossrefs

Cf. A001651.

Programs

Mathematica

a = {}; s = 0; For[n = 1, n < 40, n++, If[Length[Intersection[{Mod[n, 3]}, {1,2}]] > 0, s = s + 2^(n - 1); AppendTo[a, s]]]; a

Formula

Empirical g.f.: x*(2*x+1) / ((x-1)*(8*x^2-1)). - Colin Barker, Sep 01 2013

Extensions

Edited by Stefan Steinerberger, Jul 23 2007