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Denominators of partial sums of Catalan numbers scaled by powers of -1/20.
4

%I #2 Mar 31 2012 13:20:12

%S 1,20,200,1600,80000,1600000,16000000,1280000000,512000000,

%T 256000000000,2560000000000,102400000000000,1024000000000000,

%U 4096000000000000,40960000000000000,6553600000000000000

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

%C Numerators are given under A120791.

%F 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.

%K nonn,easy,frac

%O 0,2

%A _Wolfdieter Lang_, Jul 20 2006