A317711 - OEIS

A317711

Numbers that are not uniform tree numbers.

12, 18, 20, 24, 28, 37, 40, 44, 45, 48, 50, 52, 54, 56, 60, 61, 63, 68, 71, 72, 74, 75, 76, 80, 84, 88, 89, 90, 92, 96, 98, 99, 104, 107, 108, 111, 112, 116, 117, 120, 122, 124, 126, 132, 135, 136, 140, 142, 144, 147, 148, 150, 152, 153, 156, 157, 160, 162

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

OFFSET

1,1

COMMENTS

A positive integer n is a uniform tree number iff either n = 1 or n is a power of a squarefree number whose prime indices are also uniform tree numbers. A prime index of n is a number m such that prime(m) divides n.

LINKS

Table of n, a(n) for n=1..58.

EXAMPLE

The sequence of non-uniform tree numbers together with their Matula-Goebel trees begins:

12: (oo(o))

18: (o(o)(o))

20: (oo((o)))

24: (ooo(o))

28: (oo(oo))

37: ((oo(o)))

40: (ooo((o)))

44: (oo(((o))))