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 A329969 #4 Nov 26 2019 20:06:16
%S A329969 1,3,7,25,56,484,883,9643,32497,344277,678580,13364806,27644449,
%T A329969 582379763,3257283507,28924878925,82864869820,2320283069804,
%U A329969 5832742205075,159175049844787,1283043441049111,10423261367890565,44152005855084368,1678303577387465300,9478188244330160181
%N A329969 a(n) = Sum_{k=1..n} Stirling2(n,k) * gcd(n,k).
%t A329969 a[n_] := Sum[StirlingS2[n, k] GCD[n, k], {k, 1, n}]; Table[a[n], {n, 1, 25}]
%Y A329969 Cf. A003989, A008277, A159068.
%K A329969 nonn
%O A329969 1,2
%A A329969 _Ilya Gutkovskiy_, Nov 26 2019