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 A340474 #3 Jan 09 2021 07:51:59 %S A340474 1,1,3,22,209,2756,43717,839686,18581425,470707192,13352676101, %T A340474 420875581754,14566375690297,549877190829604,22472783629465093, %U A340474 989043215802778966,46631075599107558113,2345376059569552767344,125350843842721213505029,7095169059445749303612946 %N A340474 a(n) = n! [x^n] LW(T(x)), where T(x) = -W(-x) Euler's tree function, W(x) is the Lambert W function, and LW(x) = W(-W(x))/(-W(x)) (A340473). %p A340474 W := x -> LambertW(x): T := x -> -W(-x): LW := x -> W(-W(x))/(-W(x)): %p A340474 ser := series(LW(T(x)), x, 24): seq(n!*coeff(ser, x, n), n=0..19); %Y A340474 Cf. A340473, A097174, A177885, A207833, A227176. %Y A340474 Cf. A000169, A000272. %K A340474 nonn %O A340474 0,3 %A A340474 _Peter Luschny_, Jan 09 2021