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 A219781 #22 Jul 14 2014 12:24:09
%S A219781 3,5,7,6,9,7,2,7,4,8,1,3,1,6,9,4,8,5,6,5,3,9,5,1,9,7,8,4,8,5,6,3,7,4,
%T A219781 5,3,7,5,2,8,4,0,5,3,6,5,2,3,5,2,2,2,3,0,7,7,3,6,9,7,2,7,3,7,6,1,2,6,
%U A219781 1,7,5,8,2,7,8,1,1,1,2,7,1,7,5,7,3,0,2
%N A219781 Decimal expansion of Sum_{n = -infinity..infinity} 5^(n/2)*((1+sqrt(5))/2)^(-n^2).
%C A219781 Constant is associated with A135961.
%e A219781 3.5769727481316948565395...
%t A219781 RealDigits[N[Sum[5^(k/2)*((1+Sqrt[5])/2)^(-k^2), {k,-Infinity,Infinity}], 131], 10, 130][[1]]
%Y A219781 Cf. A135961, A135741.
%K A219781 nonn,cons
%O A219781 1,1
%A A219781 _Vaclav Kotesovec_, Nov 29 2012