A258592 Values of k such that the number of rooted trees with k nodes (A000081(k)) is even.

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, 46, 47, 48, 51, 52, 53, 54, 55, 57, 58, 59, 60, 62, 63, 66, 69, 70, 72, 79, 80, 81, 83, 85, 86, 88, 89, 90, 91, 92, 94, 95, 96, 97, 100, 101, 102, 103, 105, 106, 107

Offset: 1

Author

Vladimir Reshetnikov, Nov 06 2015

Keywords

• nonn

Comments

Complement of A263831.

Links

• G. C. Greubel, Table of n, a(n) for n = 1..5000

Crossrefs

Cf. A000081, A211192, A263831.

Programs

Mathematica

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 *)