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 A258592 #14 Mar 01 2019 17:13:50
%S A258592 0,3,4,6,7,9,11,12,13,19,20,21,24,26,29,31,32,34,36,37,39,41,43,44,45,
%T A258592 46,47,48,51,52,53,54,55,57,58,59,60,62,63,66,69,70,72,79,80,81,83,85,
%U A258592 86,88,89,90,91,92,94,95,96,97,100,101,102,103,105,106,107
%N A258592 Values of k such that the number of rooted trees with k nodes (A000081(k)) is even.
%C A258592 Complement of A263831.
%H A258592 G. C. Greubel, <a href="/A258592/b258592.txt">Table of n, a(n) for n = 1..5000</a>
%t A258592 Module[{t}, t[1] = 1; t[k_] := t[k] = Sum[DivisorSum[k-m, t[#] # &] t[m]/(k-1), {m, k-1}]; Select[Range[0, 107], EvenQ@t[#] &]] (* after _Alois P. Heinz_ *)
%Y A258592 Cf. A000081, A211192, A263831.
%K A258592 nonn
%O A258592 1,2
%A A258592 _Vladimir Reshetnikov_, Nov 06 2015