A298540 - OEIS

A298540

Matula-Goebel numbers of rooted trees such that every branch of the root has a different number of nodes.

1, 2, 3, 5, 6, 7, 10, 11, 13, 14, 15, 17, 19, 21, 22, 23, 26, 29, 30, 31, 33, 34, 37, 38, 39, 41, 42, 43, 46, 47, 51, 53, 55, 57, 58, 59, 61, 62, 65, 66, 67, 69, 71, 73, 74, 77, 78, 79, 82, 83, 85, 86, 87, 89, 91, 93, 94, 95, 97, 101, 102, 103, 106, 107, 109

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

LINKS

Table of n, a(n) for n=1..65.

EXAMPLE

Sequence of trees begins:

1 o

2 (o)

3 ((o))

5 (((o)))

6 (o(o))

7 ((oo))

10 (o((o)))

11 ((((o))))

13 ((o(o)))

14 (o(oo))

15 ((o)((o)))

17 (((oo)))

19 ((ooo))

21 ((o)(oo))

22 (o(((o))))

23 (((o)(o)))

26 (o(o(o)))

29 ((o((o))))

30 (o(o)((o)))

MATHEMATICA

nn=500;

primeMS[n_]:=If[n===1, {}, Flatten[Cases[FactorInteger[n], {p_, k_}:>Table[PrimePi[p], {k}]]]];

MGweight[n_]:=If[n===1, 1, 1+Total[MGweight/@primeMS[n]]];

Select[Range[nn], UnsameQ@@MGweight/@primeMS[#]&]

CROSSREFS

Cf. A000081, A007097, A061775, A111299, A214577, A276625, A290760, A291442, A297571, A298479, A298534, A298536, A298538, A298539.

Sequence in context: A144338 A077377 A076786 * A326535 A358977 A284892

Adjacent sequences: A298537 A298538 A298539 * A298541 A298542 A298543

KEYWORD

nonn

AUTHOR

Gus Wiseman, Jan 21 2018

STATUS

approved