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 A309911 #7 Aug 23 2019 14:09:54
%S A309911 1,3,7,25,71,360,1310,7195,35740,213318,1132154,8409475,50344672,
%T A309911 366939569,2728237607,21375289293,159969524749,1462761108082,
%U A309911 11896122581676,107011124829787,1031744001100166,9684995830526129,91735916202054984,1010641832989185386,10131466944871497886
%N A309911 a(n) = Sum_{k=1..n} Stirling2(n,k) * floor(n/k).
%F A309911 a(n) = [x^n] (1/(1 - x)) * Sum_{k=1..n} Stirling2(n,k) * x^k/(1 - x^k).
%F A309911 a(n) = Sum_{k=1..n} Sum_{d|k} Stirling2(n,d).
%t A309911 Table[Sum[StirlingS2[n, k] Floor[n/k] , {k, 1, n}], {n, 1, 25}]
%t A309911 Table[SeriesCoefficient[1/(1 - x) Sum[StirlingS2[n, k] x^k/(1 - x^k), {k, 1, n}], {x, 0, n}], {n, 1, 25}]
%t A309911 Table[Sum[Sum[StirlingS2[n, d], {d, Divisors[k]}], {k, 1, n}], {n, 1, 25}]
%o A309911 (PARI) a(n) = sum(k=1, n, stirling(n, k, 2) * (n\k)); \\ _Michel Marcus_, Aug 23 2019
%Y A309911 Cf. A008277, A308037, A308812, A309910.
%K A309911 nonn
%O A309911 1,2
%A A309911 _Ilya Gutkovskiy_, Aug 22 2019