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 A277485 #8 Nov 10 2017 07:37:26
%S A277485 0,1,6,33,216,1865,21228,303765,5222864,104540337,2383558740,
%T A277485 60933722069,1725392415288,53590463856345,1811281159509500,
%U A277485 66172416761172885,2598298697830360992,109116931783034360801,4880122696811960470692,231565260558289051906965
%N A277485 E.g.f.: -exp(2*x)*LambertW(-x).
%H A277485 G. C. Greubel, <a href="/A277485/b277485.txt">Table of n, a(n) for n = 0..385</a>
%F A277485 a(n) = Sum_{m=1..n} (binomial(n,m) * Sum_{k=1..m} binomial(m,k)*k^(k-1)).
%F A277485 a(n) ~ exp(2*exp(-1)) * n^(n-1).
%t A277485 CoefficientList[Series[-Exp[2*x]*LambertW[-x], {x, 0, 20}], x]*Range[0, 20]!
%t A277485 Table[Sum[Binomial[n, m]*Sum[Binomial[m, k]*k^(k-1), {k, 1, m}], {m, 1, n}], {n, 0, 20}]
%o A277485 (PARI) x='x+O('x^50); concat([0], Vec(serlaplace(- exp(2*x)*lambertw(-x) ))) \\ _G. C. Greubel_, Nov 08 2017
%Y A277485 Cf. A000169, A069856, A086331, A277457, A277473, A277474.
%K A277485 nonn
%O A277485 0,3
%A A277485 _Vaclav Kotesovec_, Oct 17 2016