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 A120999 #3 Mar 31 2012 13:20:12 %S A120999 1,49,2401,117649,823543,40353607,13841287201,678223072849, %T A120999 33232930569601,1628413597910449,79792266297612001,558545864083284007, %U A120999 27368747340080916343,9387480337647754305649,459986536544739960976801 %N A120999 Denominators of partial sums of Catalan numbers scaled by powers of 1/7^2 = 1/49. %C A120999 Numerators are given under A120998. %C A120999 This is the third member (p=2) 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 A120999 See A120998 for more details and a W. Lang link there for the definition of four p-families of such scaled Catalan sums. %F A120999 a(n)=denominator(r(n)) with r(n) := rI(p=2,n) = sum(C(k)/L(4)^(2*k),k=0..n), with Lucas L(4)=7 and C(k):=A000108(k) (Catalan). The rationals r(n) are given in lowest terms. %e A120999 Rationals r(n): [1, 50/49, 2452/2401, 120153/117649, 841073/823543, %e A120999 41212583/40353607, 14135916101/13841287201,...]. %K A120999 nonn,frac,easy %O A120999 0,2 %A A120999 _Wolfdieter Lang_, Aug 16 2006