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 A135755 #7 Nov 27 2017 07:42:50
%S A135755 1,2,6,40,860,63000,14714728,10562062112,22960880409360,
%T A135755 150300904214651680,2955814683617734854752,
%U A135755 174481716707875308905153664,30905247968182392588500030233024
%N A135755 a(n) = Sum_{k=0..n} C(n,k)*3^[k*(k-1)/2].
%H A135755 G. C. Greubel, <a href="/A135755/b135755.txt">Table of n, a(n) for n = 0..49</a>
%F A135755 a(n) ~ 3^(n*(n-1)/2). - _Vaclav Kotesovec_, Nov 27 2017
%t A135755 Table[Sum[Binomial[n, k]*3^(Binomial[k, 2]), {k,0,n}], {n,0,10}] (* _G. C. Greubel_, Nov 07 2016 *)
%o A135755 (PARI) {a(n)=sum(k=0,n,binomial(n,k)*3^(k*(k-1)/2))}
%Y A135755 Cf. variants: A006896, A135756.
%K A135755 nonn
%O A135755 0,2
%A A135755 _Paul D. Hanna_, Nov 27 2007