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 A228047 #17 Feb 24 2025 04:37:28
%S A228047 4,2,3,5,3,9,0,9,9,6,0,8,7,0,0,1,9,6,8,3,7,6,0,7,6,8,9,9,7,4,4,2,8,9,
%T A228047 3,7,5,4,4,3,2,2,8,8,1,8,9,4,1,7,1,1,1,0,2,1,7,5,6,0,8,4,2,8,1,3,0,9,
%U A228047 3,4,7,8,2,4,5,8,2,6,7,1,1,7,8,2,5,9
%N A228047 Decimal expansion of sum of reciprocals of row 5 of the natural number array, A185787.
%C A228047 See A228044.
%F A228047 Equals 1/15 + 1/20 + 1/26 + ...
%F A228047 Equals (1/17160)*(-9997 + 1760*r*tanh(r)), where r = (Pi/2)*sqrt(39).
%e A228047 0.42353909960870019683760768997442893...
%t A228047 $MaxExtraPrecision = Infinity; t[n_, k_] := t[n, k] = n + (n + k - 2) (n + k - 1)/2; u = N[Sum[1/t[5, k], {k, 1, Infinity}], 130]; RealDigits[u, 10]
%o A228047 (PARI) sumnumrat(1/(n*(n+7)/2+11),1) \\ _Charles R Greathouse IV_, Feb 08 2023
%Y A228047 Cf. A185787, A000027, A228044, A226985.
%K A228047 nonn,cons,easy
%O A228047 0,1
%A A228047 _Clark Kimberling_, Aug 06 2013