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 A226121 #18 Feb 16 2025 08:33:19
%S A226121 1,1,9,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
%T A226121 9,5,9,3,7,4,5,8,5,1,0,2,5,5,4,7,3,3,5,5,8,8,5,8,4,9,1,3,3,9,7,3,8,4,
%U A226121 1,5,0,4,3,3,9,1,5,8,0,5,4,1,2,7,9,3,5,1,5,8,7,8,5,1,6,5,4,2,3,2
%N A226121 Decimal expansion of sum_{n=1..infinity} n^3/(exp(2*Pi*n/13)-1).
%C A226121 An almost-integer discovered by Simon Plouffe. The computed sum equals 119 within 31 digits after the decimal point.
%H A226121 Simon Plouffe, <a href="http://www.plouffe.fr">Simon Plouffe Home Page</a>
%H A226121 Eric Weisstein's MathWorld, <a href="https://mathworld.wolfram.com/AlmostInteger.html">Almost Integer</a>
%e A226121 119.0000000000000000000000000000000959374585102554733558858491339738415043391...
%t A226121 NSum[n^3/(Exp[2*Pi*n/13] - 1), {n, 1, Infinity}, NSumTerms -> 500, WorkingPrecision -> 100] // RealDigits[#, 10, 100] & // First
%Y A226121 Cf. A060295 (a famous almost-integer: Ramanujan's constant), A226120 (another surprising almost-integer by Simon Plouffe).
%K A226121 nonn,cons
%O A226121 3,3
%A A226121 _Jean-François Alcover_, May 27 2013
%E A226121 Offset corrected by _Rick L. Shepherd_, Jan 01 2014