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 A298120 Matula-Goebel numbers of rooted trees in which all positive outdegrees are odd. 9
 1, 2, 3, 5, 8, 11, 12, 18, 19, 20, 27, 30, 31, 32, 37, 44, 45, 48, 50, 61, 66, 67, 71, 72, 75, 76, 80, 99, 103, 108, 110, 113, 114, 120, 124, 125, 127, 128, 131, 148, 157, 162, 165, 171, 176, 180, 186, 190, 192, 193, 197, 200, 222, 223, 229, 242, 243, 244, 264 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS EXAMPLE Sequence of trees begins: 1  o 2  (o) 3  ((o)) 5  (((o))) 8  (ooo) 11 ((((o)))) 12 (oo(o)) 18 (o(o)(o)) 19 ((ooo)) 20 (oo((o))) 27 ((o)(o)(o)) 30 (o(o)((o))) 31 (((((o))))) 32 (ooooo) 37 ((oo(o))) 44 (oo(((o)))) 45 ((o)(o)((o))) 48 (oooo(o)) 50 (o((o))((o))) MATHEMATICA primeMS[n_]:=If[n===1, {}, Flatten[Cases[FactorInteger[n], {p_, k_}:>Table[PrimePi[p], {k}]]]]; otQ[n_]:=Or[n===1, With[{m=primeMS[n]}, OddQ@Length@m&&And@@otQ/@m]]; Select[Range[1000], otQ] CROSSREFS Cf. A000081, A007097, A026424, A061775, A214577, A276625, A277098, A290760, A291441, A291442, A291636, A297571, A298118. Sequence in context: A173672 A303024 A070223 * A298205 A117725 A106637 Adjacent sequences:  A298117 A298118 A298119 * A298121 A298122 A298123 KEYWORD nonn AUTHOR Gus Wiseman, Jan 12 2018 STATUS approved

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Last modified April 6 16:14 EDT 2020. Contains 333276 sequences. (Running on oeis4.)