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 A377331 #9 Oct 25 2024 09:25:20
%S A377331 1,7,58,707,11186,219202,5097205,137036819,4179577045,142539843882,
%T A377331 5374034016858,221930535785918,9962431381720780,482997720973917947,
%U A377331 25151350530268841003,1400042027334939211235,82960609980815501293708,5213812927633674297808237,346394632975721545946690108
%N A377331 a(n) = Sum_{k=1..n} binomial(n,k) * sigma(k,n).
%F A377331 a(n) ~ n^n / (sqrt(1 + LambertW(exp(-1))) * exp(n) * LambertW(exp(-1))^n).
%t A377331 Table[Sum[Binomial[n, k] * DivisorSigma[n, k], {k, 1, n}], {n, 1, 20}]
%o A377331 (PARI) {a(n)=sum(k=1, n, binomial(n, k)*sigma(k, n))}
%Y A377331 Cf. A109974, A205812.
%K A377331 nonn
%O A377331 1,2
%A A377331 _Vaclav Kotesovec_, Oct 25 2024