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A322553
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Odd numbers whose product of prime indices is a prime power.
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1
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1, 3, 5, 7, 9, 11, 17, 19, 21, 23, 25, 27, 31, 41, 49, 53, 57, 59, 63, 67, 81, 83, 97, 103, 109, 115, 121, 125, 127, 131, 133, 147, 157, 159, 171, 179, 189, 191, 211, 227, 241, 243, 277, 283, 289, 311, 331, 343, 353, 361, 367, 371, 393, 399, 401, 419, 431, 441
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OFFSET
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1,2
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COMMENTS
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Differs from A322400 in having 1 and lacking 377, the MM-number of {{1,2},{1,3}}.
A prime index of n is a number m such that prime(m) divides n. The multiset of prime indices of n is row n of A112798.
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LINKS
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EXAMPLE
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The multiset multisystem with MM-number n is formed by taking the multiset of prime indices of each part of the multiset of prime indices of n. For example, the prime indices of 78 are {1,2,6}, so the multiset multisystem with MM-number 78 is {{},{1},{1,2}}. The sequence of multiset partitions whose MM-numbers belong to this sequence begins:
1: {}
3: {{1}}
5: {{2}}
7: {{1,1}}
9: {{1},{1}}
11: {{3}}
17: {{4}}
19: {{1,1,1}}
21: {{1},{1,1}}
23: {{2,2}}
25: {{2},{2}}
27: {{1},{1},{1}}
31: {{5}}
41: {{6}}
49: {{1,1},{1,1}}
53: {{1,1,1,1}}
57: {{1},{1,1,1}}
59: {{7}}
63: {{1},{1},{1,1}}
67: {{8}}
81: {{1},{1},{1},{1}}
83: {{9}}
97: {{3,3}}
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MATHEMATICA
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primeMS[n_]:=If[n==1, {}, Flatten[Cases[FactorInteger[n], {p_, k_}:>Table[PrimePi[p], {k}]]]];
Select[Range[1, 100, 2], #==1||PrimePowerQ[Times@@primeMS[#]]&]
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PROG
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(PARI) isok(n) = {if (n % 2, my(f = factor(n), pk = prod(k=1, #f~, primepi(f[k, 1]))); (pk == 1) || isprimepower(pk); ); } \\ Michel Marcus, Dec 16 2018
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CROSSREFS
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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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