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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A304686 Numbers with strictly decreasing prime multiplicities. 2
1, 2, 3, 4, 5, 7, 8, 9, 11, 12, 13, 16, 17, 19, 20, 23, 24, 25, 27, 28, 29, 31, 32, 37, 40, 41, 43, 44, 45, 47, 48, 49, 52, 53, 56, 59, 61, 63, 64, 67, 68, 71, 72, 73, 76, 79, 80, 81, 83, 88, 89, 92, 96, 97, 99, 101, 103, 104, 107, 109, 112, 113, 116, 117, 121 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

EXAMPLE

10 = 2*5 has prime multiplicities (1,1) so is not in the sequence.

20 = 2*2*5 has prime multiplicities (2,1) so is in the sequence

90 = 2*3*3*5 has prime multiplicities (1,2,1) so is not in the sequence.

MATHEMATICA

Select[Range[200], Greater@@FactorInteger[#][[All, 2]]&]

PROG

(PARI) isok(n) = my(vm = factor(n)[, 2]); vm == vecsort(vm, , 4) && (#vm == #Set(vm)); \\ Michel Marcus, May 17 2018

CROSSREFS

Cf. A001221, A001222, A001597, A005117, A055932, A071365, A112769, A130091, A133808, A133811, A181819, A242031, A304678, A304679, A283050.

Sequence in context: A268375 A048683 A231876 * A085233 A133813 A326836

Adjacent sequences:  A304683 A304684 A304685 * A304687 A304688 A304689

KEYWORD

nonn

AUTHOR

Gus Wiseman, May 16 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 October 14 09:25 EDT 2019. Contains 327995 sequences. (Running on oeis4.)