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A327901
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Nonprime squarefree numbers whose prime indices all have the same sum of prime indices (A056239).
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3
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1, 35, 143, 209, 247, 391, 493, 629, 667, 851, 901, 1073, 1219, 1333, 1457, 1537, 1891, 1961, 2021, 2201, 2623, 2717, 2759, 2867, 2993, 3053, 3239, 3337, 3827, 3977, 4061, 4183, 4223, 4331, 4387, 4633, 5429, 5633, 5767, 5959, 6157, 6191, 6319, 7081, 7093, 7519
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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.
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LINKS
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EXAMPLE
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The sequence of terms together with their prime indices begins:
1: {}
35: {3,4}
143: {5,6}
209: {5,8}
247: {6,8}
391: {7,9}
493: {7,10}
629: {7,12}
667: {9,10}
851: {9,12}
901: {7,16}
1073: {10,12}
1219: {9,16}
1333: {11,14}
1457: {11,15}
1537: {10,16}
1891: {11,18}
1961: {12,16}
2021: {14,15}
2201: {11,20}
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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[1000], !PrimeQ[#]&&SquareFreeQ[#]&&SameQ@@Total/@primeMS/@primeMS[#]&];
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CROSSREFS
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The version including primes and nonsquarefree numbers is A326534.
The version for number of prime indices is A327900.
The version for mean of prime indices is A327902.
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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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