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A304678
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Numbers with weakly increasing prime multiplicities.
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31
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1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 25, 26, 27, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 41, 42, 43, 46, 47, 49, 50, 51, 53, 54, 55, 57, 58, 59, 61, 62, 64, 65, 66, 67, 69, 70, 71, 73, 74, 75, 77, 78, 79, 81, 82, 83
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OFFSET
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1,2
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COMMENTS
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LINKS
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EXAMPLE
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12 = 2*2*3 has prime multiplicities (2,1) so is not in the sequence.
36 = 2*2*3*3 has prime multiplicities (2,2) so is in the sequence.
150 = 2*3*5*5 has prime multiplicities (1,1,2) so is in the sequence.
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MAPLE
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q:= n-> (l-> (t-> andmap(i-> l[i, 2]<=l[i+1, 2],
[$1..t-1]))(nops(l)))(sort(ifactors(n)[2])):
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MATHEMATICA
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Select[Range[200], OrderedQ[FactorInteger[#][[All, 2]]]&]
Select[Range[90], Min[Differences[FactorInteger[#][[;; , 2]]]]>=0&] (* Harvey P. Dale, Jan 28 2024 *)
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PROG
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(PARI) isok(n) = my(vm = factor(n)[, 2]); vm == vecsort(vm); \\ Michel Marcus, May 17 2018
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CROSSREFS
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Cf. A001221, A001222, A071365, A112769, A130091, A133808, A133811, A242031, A304465, A304679, A304687.
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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