A120796 Denominators of partial sums of Catalan numbers scaled by powers of -1/20.

1, 20, 200, 1600, 80000, 1600000, 16000000, 1280000000, 512000000, 256000000000, 2560000000000, 102400000000000, 1024000000000000, 4096000000000000, 40960000000000000, 6553600000000000000

Offset: 0

Author

Wolfdieter Lang, Jul 20 2006

Keywords

• nonn
• easy
• frac

Comments

Numerators are given under A120791.

Formula

a(n)=denominator(r(n)), with the rationals r(n):=sum(((-1)^k)*C(k)/20^k,k=0..n) with C(k):=A000108(k) (Catalan numbers). Rationals r(n) are taken in lowest terms.