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 A277501 #7 Nov 10 2017 07:37:57
%S A277501 0,1,2,7,48,461,5488,79171,1347328,26396185,585025024,14473813311,
%T A277501 395433660416,11824374817893,384118189803520,13470784014801787,
%U A277501 507233444671848448,20411081546839908401,874130806090067607552,39696948293418345150327
%N A277501 E.g.f.: -LambertW(-tanh(x)).
%H A277501 G. C. Greubel, <a href="/A277501/b277501.txt">Table of n, a(n) for n = 0..389</a>
%F A277501 a(n) ~ sqrt(1-exp(-2)) * 2^(n-1/2) * (log((exp(1)+1)/(exp(1)-1)))^(1/2-n) * exp(1/2-n) * n^(n-1).
%t A277501 CoefficientList[Series[-LambertW[-Tanh[x]], {x, 0, 20}], x] * Range[0, 20]!
%o A277501 (PARI) x='x+O('x^10); concat([0], Vec(serlaplace(-lambertw(-tanh(x))))) \\ _G. C. Greubel_, Nov 09 2017
%Y A277501 Cf. A238085, A277468, A277480, A277500.
%K A277501 nonn
%O A277501 0,3
%A A277501 _Vaclav Kotesovec_, Oct 18 2016