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

1,2

Comments

Complement of A258592.

Links

Table of n, a(n) for n=1..61.

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 *)

Crossrefs

Cf. A000081, A211192, A258592.

Sequence in context: A100829 A030713 A219222 * A189457 A189362 A189928

Adjacent sequences: A263828 A263829 A263830 * A263832 A263833 A263834

Keyword

nonn

Author

Vladimir Reshetnikov, Nov 03 2015

Status

approved