A263831 Values of k such that the number of rooted trees with k nodes (A000081(k)) is odd.

1, 2, 5, 8, 10, 14, 15, 16, 17, 18, 22, 23, 25, 27, 28, 30, 33, 35, 38, 40, 42, 49, 50, 56, 61, 64, 65, 67, 68, 71, 73, 74, 75, 76, 77, 78, 82, 84, 87, 93, 98, 99, 104, 108, 113, 114, 115, 117, 118, 119, 120, 121, 122, 123, 124, 127, 128, 135, 137, 138, 139

Offset: 1

Author

Vladimir Reshetnikov, Nov 03 2015

Keywords

• nonn

Comments

Complement of A258592.

Crossrefs

Cf. A000081, A211192, A258592.

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[140], OddQ@t[#] &]] (* after Alois P. Heinz *)