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Search: id:A097320
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| A097320 |
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Numbers with more than one prime factor and, in the ordered factorization, the exponent always decreases when read from left to right. |
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+0
4
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| 12, 20, 24, 28, 40, 44, 45, 48, 52, 56, 63, 68, 72, 76, 80, 88, 92, 96, 99, 104, 112, 116, 117, 124, 135, 136, 144, 148, 152, 153, 160, 164, 171, 172, 175, 176, 184, 188, 189, 192, 200, 207, 208, 212, 224, 232, 236, 244, 248, 261, 268, 272, 275, 279, 284, 288
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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If n = Sum[k=1..m, p(k)^e(k)], then k>1, e(1) > e(2) >...> e(m).
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EXAMPLE
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80 is 2^4 * 5^1, and 4>1, so 80 is in sequence.
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PROGRAM
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(PARI) for(n=1, 320, F=factor(n):t=0:s=matsize(F)[1]: if(s>1, for(k=1, s-1, if(F[k, 2]<=F[k+1, 2], t=1:break)): if(!t, print1(n", "))))
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CROSSREFS
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Subset of A005117 and A097318 and A112769. Cf. A097319.
Adjacent sequences: A097317 A097318 A097319 this_sequence A097321 A097322 A097323
Sequence in context: A065201 A136724 A112769 this_sequence A111592 A111947 A109396
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KEYWORD
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nonn
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AUTHOR
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Ralf Stephan, Aug 04 2004
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