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 A273442 #10 Aug 28 2017 12:12:48
%S A273442 1,3,95,5595,484729,55545735,7923937307,1353285904971,269240651261153,
%T A273442 61157779792168059,15617503320899550135,4429016799173481942427,
%U A273442 1381112305978592892946825,469689278931628969590283855,173002815169302537782725771395
%N A273442 Number of endofunctions on [2n] with exactly n cycles.
%H A273442 Alois P. Heinz, <a href="/A273442/b273442.txt">Table of n, a(n) for n = 0..288</a>
%F A273442 a(n) = (2*n)!/n! * [x^(2*n)] (-log(1+LambertW(-x)))^n.
%F A273442 a(n) = A060281(2n,n).
%F A273442 a(n) ~ c * d^n * n^(n-1/2), where d = 2^(4-r) * exp(1-r) * (2-r)^(r-2) * log(s) / (1-1/s)^r = 10.40858458700790823344027277763248832..., where r = 1.2672171362228848078038115564503589940694831794020694762759870935... is the root of the equation r*log(s) * (-1 + (r-s)* log((2*(s-1))/(s*(2-r)))) = 1 - s, where s = -r*LambertW(-1, -exp(-1/r)/r) = 1.5782614856055967129193228312616913... and c = 0.336740238865974324583136447665761... - _Vaclav Kotesovec_, Nov 01 2016, extended Aug 28 2017
%t A273442 Table[(2*n)!/n! * SeriesCoefficient[(-Log[1+LambertW[-x]])^n, {x, 0, 2*n}], {n, 0, 20}] (* _Vaclav Kotesovec_, Nov 01 2016 *)
%t A273442 Flatten[{1, Table[Sum[Binomial[2*n-1, k] * (2*n)^(2*n-1-k) * Abs[StirlingS1[k+1, n]], {k, 0, 2*n-1}], {n, 1, 20}]}] (* _Vaclav Kotesovec_, Nov 01 2016 *)
%Y A273442 Cf. A060281.
%K A273442 nonn
%O A273442 0,2
%A A273442 _Alois P. Heinz_, May 22 2016