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A320458
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MM-numbers of labeled simple graphs spanning an initial interval of positive integers.
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13
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1, 13, 377, 611, 1363, 1937, 2021, 2117, 16211, 17719, 26273, 27521, 44603, 56173, 58609, 83291, 91031, 91039, 99499, 141401, 143663, 146653, 147533, 153023, 159659, 167243, 170839, 203087, 237679, 243893, 265369, 271049, 276877, 290029, 301129, 315433, 467711
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OFFSET
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1,2
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COMMENTS
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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. 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}}.
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LINKS
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EXAMPLE
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The sequence of terms together with their multiset multisystems begins:
1: {}
13: {{1,2}}
377: {{1,2},{1,3}}
611: {{1,2},{2,3}}
1363: {{1,3},{2,3}}
1937: {{1,2},{3,4}}
2021: {{1,4},{2,3}}
2117: {{1,3},{2,4}}
16211: {{1,2},{1,3},{1,4}}
17719: {{1,2},{1,3},{2,3}}
26273: {{1,2},{1,4},{2,3}}
27521: {{1,2},{1,3},{2,4}}
44603: {{1,2},{2,3},{2,4}}
56173: {{1,2},{1,3},{3,4}}
58609: {{1,3},{1,4},{2,3}}
83291: {{1,2},{1,4},{3,4}}
91031: {{1,3},{1,4},{2,4}}
91039: {{1,2},{2,3},{3,4}}
99499: {{1,3},{2,3},{2,4}}
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MATHEMATICA
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primeMS[n_]:=If[n==1, {}, Flatten[Cases[FactorInteger[n], {p_, k_}:>Table[PrimePi[p], {k}]]]];
normQ[sys_]:=Or[Length[sys]==0, Union@@sys==Range[Max@@Max@@sys]];
Select[Range[10000], And[SquareFreeQ[#], normQ[primeMS/@primeMS[#]], And@@(And[SquareFreeQ[#], Length[primeMS[#]]==2]&/@primeMS[#])]&]
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CROSSREFS
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Cf. A001222, A003963, A005117, A055932, A056239, A112798, A255906, A290103, A302242, A302478, A302491, A305052.
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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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