A120997 Denominators of partial sums of Catalan numbers scaled by powers of 1/9.

1, 9, 81, 729, 6561, 19683, 177147, 1594323, 43046721, 387420489, 3486784401, 31381059609, 282429536481, 2541865828329, 2541865828329, 22876792454961, 205891132094649, 5559060566555523, 50031545098999707

Offset: 0

Author

Wolfdieter Lang, Aug 16 2006

Keywords

• nonn
• frac
• easy

Comments

Numerators are given under A120996.

See A120996 for details and a W. Lang link found there for the definition of four p-families of such scaled Catalan sums.

Formula

a(n)=denominator(r(n)) with r(n) := rI(p=1,n) = sum(C(k)/L(2)^(2*k),k=0..n), with Lucas L(2)=3 and C(k):=A000108(k) (Catalan).