A131093 a(1)=1, a(n) = a(n-1) + sum of odd numbers which are among the first (n-1) terms of the sequence.

1, 2, 3, 7, 18, 29, 69, 178, 287, 683, 1762, 2841, 6761, 17442, 28123, 66927, 172658, 278389, 662509, 1709138, 2755767, 6558163, 16918722, 27279281, 64919121, 167478082, 270037043, 642633047, 1657862098, 2673091149

Offset: 1

Author

Reinhard Zumkeller, Jun 14 2007

Keywords

• nonn

Comments

a(n) mod 2 = A011655(n+1);

a(n) = a(n-1) + Sum(a(k)*(a(k) mod 2): 1<=k

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000
• Eric Weisstein's World of Mathematics, Odd Number

Crossrefs

Cf. A096777, A101135.

Programs

Mathematica

nxt[{ot_,a_}]:=Module[{x=a+ot},{If[OddQ[x],ot+x,ot],x}]; NestList[nxt,{1,1},30][[All,2]] (* Harvey P. Dale, Dec 18 2020 *)

Formula

Empirical g.f.: -x*(x-1)*(x^4+3*x^3+6*x^2+3*x+1) / (x^6-10*x^3+1). - Colin Barker, Mar 29 2013

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

Content is available under The OEIS End-User License Agreement.