A136169 a(n) = 2*a(n-1) - [(n+1)/3] for n>0 with a(0) = 1.

1, 2, 3, 5, 9, 16, 30, 58, 113, 223, 443, 882, 1760, 3516, 7027, 14049, 28093, 56180, 112354, 224702, 449397, 898787, 1797567, 3595126, 7190244, 14380480, 28760951, 57521893, 115043777, 230087544, 460175078, 920350146, 1840700281, 3681400551

Offset: 0

Author

Paul D. Hanna, Dec 23 2007

Keywords

• nonn
• easy

Links

• Index entries for linear recurrences with constant coefficients, signature (3,-2,1,-3,2).

Crossrefs

Cf. A136219.

Programs

Mathematica

nxt[{n_,a_}]:={n+1, 2a-Floor[(n+2)/3]}; NestList[nxt,{0,1},50][[All,2]] (* Harvey P. Dale, Aug 09 2021 *)

PARI

{a(n)=if(n==0,1,2*a(n-1)-((n+1)\3))}

Formula

G.f.: (1 - x^2*(1+x+x^2)/(1-x^3)^2 )/(1-2*x).