A324928 Matula-Goebel numbers of rooted trees of depth 3.

5, 10, 13, 15, 17, 20, 23, 25, 26, 30, 34, 35, 37, 39, 40, 43, 45, 46, 50, 51, 52, 60, 61, 65, 67, 68, 69, 70, 73, 74, 75, 78, 80, 85, 86, 89, 90, 91, 92, 95, 100, 102, 103, 104, 105, 107, 111, 115, 117, 119, 120, 122, 125, 129, 130, 134, 135, 136, 138, 140

Offset

1,1

Comments

Numbers n such that A109082(n) = 3.

Links

Table of n, a(n) for n=1..60.

Example

The sequence of all rooted trees of depth 3 together with their Matula-Goebel numbers begins:
   5: (((o)))
  10: (o((o)))
  13: ((o(o)))
  15: ((o)((o)))
  17: (((oo)))
  20: (oo((o)))
  23: (((o)(o)))
  25: (((o))((o)))
  26: (o(o(o)))
  30: (o(o)((o)))
  34: (o((oo)))
  35: (((o))(oo))
  37: ((oo(o)))
  39: ((o)(o(o)))
  40: (ooo((o)))
  43: ((o(oo)))
  45: ((o)(o)((o)))
  46: (o((o)(o)))
  50: (o((o))((o)))
  51: ((o)((oo)))
  52: (oo(o(o)))
  60: (oo(o)((o)))

Mathematica

Select[Range[100], Length[NestWhileList[Times@@PrimePi/@FactorInteger[#][[All, 1]]&, #, #>1&]]-1==3&]

Crossrefs

Cf. A000081, A003963, A007097, A102378, A318400, A324927, A324930.

Sequence in context: A226386 A200995 A049197 * A009000 A198389 A057100

Adjacent sequences: A324925 A324926 A324927 * A324929 A324930 A324931

Keyword

nonn

Author

Gus Wiseman, Mar 21 2019

Status

approved