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

1,2

Comments

Complement of A263831.

Links

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

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 *)

Crossrefs

Cf. A000081, A211192, A263831.

Sequence in context: A123540 A065313 A103566 * A018825 A247779 A243989

Adjacent sequences: A258589 A258590 A258591 * A258593 A258594 A258595

Keyword

nonn

Author

Vladimir Reshetnikov, Nov 06 2015

Status

approved