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A136169 a(n) = 2*a(n-1) - [(n+1)/3] for n>0 with a(0) = 1. 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 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..33.

FORMULA

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

PROG

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

CROSSREFS

Cf. A136219.

Sequence in context: A329700 A217282 A047061 * A047041 A154223 A061031

Adjacent sequences:  A136166 A136167 A136168 * A136170 A136171 A136172

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Dec 23 2007

STATUS

approved

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Last modified April 10 18:17 EDT 2021. Contains 342853 sequences. (Running on oeis4.)