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 A255169 #15 Jul 30 2018 22:57:05
%S A255169 1,9,9,2,2,9,4,7,6,7,1,2,4,9,8,7,3,9,2,9,2,6,0,1,6,6,1,3,0,0,2,1,1,7,
%T A255169 3,8,7,8,3,1,4,0,4,5,2,3,0,6,3,7,7,0,0,6,9,5,2,3,5,0,1,6,8,4,8,4,8,1,
%U A255169 9,8,9,9,3,4,9,7,9,2,7,0,5,8
%N A255169 Decimal expansion of the sum_{n>=0} n^2/e^n = e(1+e)/(e-1)^3.
%C A255169 The expression generating this constant is a second degree Eulerian polynomial, in the "variable" e, with coefficients {1, 1}, generated from sum_{n>=0} n^m/e^n, with m=2. See A008292. It approximates m!.
%C A255169 See A098875 for the first degree polynomial and value.
%F A255169 Equals sum_{n>=0} n^2/e^n.
%e A255169 1.99229476712498....
%t A255169 Sum[n^2/Exp[n], {n, 0, Infinity}]; N[Sum[n^2/Exp[n], {n, 0, Infinity}],100]
%o A255169 (PARI) suminf(n=0, n^2/exp(n)) \\ _Michel Marcus_, Jul 30 2018
%o A255169 (PARI) exp(1)*(1+exp(1))/(exp(1)-1)^3 \\ _Altug Alkan_, Jul 30 2018
%Y A255169 Cf. A008292, A098875.
%K A255169 nonn,cons
%O A255169 1,2
%A A255169 _Richard R. Forberg_, Feb 15 2015