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 A228808 #18 Jan 19 2019 06:57:38
%S A228808 1,2,4,20,296,10067,927100,219541877,110728186648,137502766579907,
%T A228808 448577320868198789,3169529341990169816462,51243646781214826181569316,
%U A228808 2201837465728010770618930322223,215520476721579201896200887266792583,45634827026091489574547858030506357191920
%N A228808 a(n) = Sum_{k=0..n} binomial(n*k, k^2).
%C A228808 Ignoring initial term, equals the logarithmic derivative of A228809.
%C A228808 Equals row sums of triangle A228832.
%H A228808 Seiichi Manyama, <a href="/A228808/b228808.txt">Table of n, a(n) for n = 0..73</a>
%F A228808 Limit n->infinity a(n)^(1/n^2) = (1-r)^(-r/2) = 1.533628065110458582053143..., where r = A220359 = 0.70350607643066243... is the root of the equation (1-r)^(2*r-1) = r^(2*r). - _Vaclav Kotesovec_, Sep 06 2013
%e A228808 L.g.f.: L(x) = 2*x + 4*x^2/2 + 20*x^3/3 + 296*x^4/4 + 10067*x^5/5 +...
%e A228808 where
%e A228808 exp(L(x)) = 1 + 2*x + 4*x^2 + 12*x^3 + 94*x^4 + 2195*x^5 + 158904*x^6 + 31681195*x^7 +...+ A228809(n)*x^n +...
%t A228808 Table[Sum[Binomial[n*k, k^2],{k,0,n}],{n,0,15}] (* _Vaclav Kotesovec_, Sep 06 2013 *)
%o A228808 (PARI) a(n)=sum(k=0,n,binomial(n*k,k^2))
%o A228808 for(n=0,20,print1(a(n),", "))
%Y A228808 Cf. A228809, A207136, A167009, A228832.
%K A228808 nonn
%O A228808 0,2
%A A228808 _Paul D. Hanna_, Sep 04 2013