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A263831 Values of k such that the number of rooted trees with k nodes (A000081(k)) is odd. 3
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified May 20 08:03 EDT 2022. Contains 353852 sequences. (Running on oeis4.)