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A317713 Number of distinct terminal subtrees of the rooted tree with Matula-Goebel number n. 19
1, 2, 3, 2, 4, 3, 3, 2, 3, 4, 5, 3, 4, 3, 4, 2, 4, 3, 3, 4, 4, 5, 4, 3, 4, 4, 3, 3, 5, 4, 6, 2, 5, 4, 5, 3, 4, 3, 4, 4, 5, 4, 4, 5, 4, 4, 5, 3, 3, 4, 5, 4, 3, 3, 5, 3, 4, 5, 5, 4, 4, 6, 4, 2, 5, 5, 4, 4, 4, 5, 5, 3, 5, 4, 4, 3, 6, 4, 6, 4, 3, 5, 5, 4, 6, 4, 5 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..87.

Index entries for sequences related to Matula-Göbel numbers

EXAMPLE

20 is the Matula-Goebel number of the tree (oo((o))), which has 4 distinct terminal subtrees: {(oo((o))), ((o)), (o), o}. So a(20) = 4.

MATHEMATICA

ids[n_]:=Union@@FixedPointList[Union@@(Cases[If[#==1, {}, FactorInteger[#]], {p_, _}:>PrimePi[p]]&/@#)&, {n}];

Table[Length[ids[n]], {n, 100}]

CROSSREFS

Cf. A000081, A007097, A049076, A061773, A061775, A076146, A109082, A109129, A206491, A303431, A316476.

Sequence in context: A238766 A304088 A286597 * A318046 A246348 A205782

Adjacent sequences:  A317710 A317711 A317712 * A317714 A317715 A317716

KEYWORD

nonn

AUTHOR

Gus Wiseman, Aug 05 2018

STATUS

approved

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Last modified March 25 20:10 EDT 2019. Contains 321477 sequences. (Running on oeis4.)