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 A174461 #8 Jan 15 2019 10:00:55 %S A174461 1,1,3,6,21,32,174,236,1310,2609,12579,18150,150980,198821,1471346, %T A174461 2645433,17956158,24534384,234506155,304507520,2773986000,4315363549, %U A174461 36311714888,47769153478,500399410005,637747787407,6468558255893,9142971548460,88936892205131 %N A174461 G.f.: exp( Sum_{n>=1} A174462(n)*x^n/n ) where A174462(n) = Sum_{d|n} C(n,d)^2. %C A174461 Compare to the g.f. G(x) of the Catalan numbers: %C A174461 G(x)^2 = exp( Sum_{n>=1} A000984(n)*x^n/n ) where A000984(n) = Sum_{k=0..n} C(n,k)^2. %H A174461 Seiichi Manyama, <a href="/A174461/b174461.txt">Table of n, a(n) for n = 0..1671</a> %o A174461 (PARI) {a(n)=polcoeff(exp(sum(m=1,n,x^m/m*sumdiv(m,d,binomial(m,d)^2))+x*O(x^n)),n)} %Y A174461 Cf. A174462, A110448. %K A174461 nonn %O A174461 0,3 %A A174461 _Paul D. Hanna_, Apr 04 2010