This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A121001 #3 Mar 31 2012 13:20:12 %S A121001 1,324,52488,34012224,5509980288,595077871104,96402615118848, %T A121001 124937789194027008,60719765548297125888,19673204037648268787712, %U A121001 3187059054099019543609344,2065214267056164664258854912 %N A121001 Denominators of partial sums of Catalan numbers scaled by powers of 1/18^2 = 1/324. %C A121001 Numerators are given under A121000. %C A121001 This is the fourth member (p=3) of the first p-family of partial sums of normalized scaled Catalan series CsnI(p):=sum(C(k)/L(2*p)^(2*k),k=0..infinity) with limit L(2*p)*(F(2*p+1) - F(2*p)*phi) = L(2*p)/phi^(2*p), with C(n)=A000108(n) (Catalan), F(n)= A000045(n) (Fibonacci), L(n) = A000032(n) (Lucas) and phi:=(1+sqrt(5))/2 (golden section). %C A121001 See A120998 for more details and a W. Lang link there for the definition of four p-families of such scaled Catalan sums. %F A121001 a(n)=denominator(r(n)) with r(n) := rI(p=3,n) = sum(C(k)/L(6)^(2*k),k=0..n), with Lucas L(6)=18 and C(k):=A000108(k) (Catalan). The rationals r(n) are given in lowest terms. %e A121001 Rationals r(n): [1, 325/324, 52651/52488, 34117853/34012224, 5527092193/5509980288, 596925956851/595077871104, ...]. %K A121001 nonn,frac,easy %O A121001 0,2 %A A121001 _Wolfdieter Lang_, Aug 16 2006