login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A316468 Matula-Goebel numbers of locally stable rooted trees, meaning no branch is a submultiset of any other branch of the same root. 9
1, 2, 3, 4, 5, 7, 8, 9, 11, 15, 16, 17, 19, 23, 25, 27, 31, 32, 33, 35, 45, 47, 49, 51, 53, 55, 59, 64, 67, 69, 75, 77, 81, 83, 85, 93, 95, 97, 99, 103, 119, 121, 125, 127, 128, 131, 135, 137, 141, 149, 153, 155, 161, 165, 175, 177, 187, 197, 201, 207, 209 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

A prime index of n is a number m such that prime(m) divides n. A number is in the sequence iff its distinct prime indices are pairwise indivisible and already belong to the sequence.

LINKS

Table of n, a(n) for n=1..61.

EXAMPLE

Sequence of locally stable rooted trees preceded by their Matula-Goebel numbers begins:

   1: o

   2: (o)

   3: ((o))

   4: (oo)

   5: (((o)))

   7: ((oo))

   8: (ooo)

   9: ((o)(o))

  11: ((((o))))

  15: ((o)((o)))

  16: (oooo)

  17: (((oo)))

  19: ((ooo))

  23: (((o)(o)))

  25: (((o))((o)))

  27: ((o)(o)(o))

  31: (((((o)))))

MATHEMATICA

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

Select[Range[100], Or[#==1, And[Select[Tuples[primeMS[#], 2], UnsameQ@@#&&Divisible@@#&]=={}, And@@#0/@primeMS[#]]]&]

CROSSREFS

Cf. A000081, A004111, A007097, A112798, A277098, A285572, A285573, A303362, A304713, A316467, A316470, A316473, A316475, A316476, A316495.

Sequence in context: A282136 A153730 A140691 * A099627 A184155 A318612

Adjacent sequences:  A316465 A316466 A316467 * A316469 A316470 A316471

KEYWORD

nonn

AUTHOR

Gus Wiseman, Jul 04 2018

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified February 19 07:51 EST 2019. Contains 320309 sequences. (Running on oeis4.)