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A359913
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Numbers whose multiset of prime factors has integer median.
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11
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2, 3, 4, 5, 7, 8, 9, 11, 12, 13, 15, 16, 17, 18, 19, 20, 21, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 37, 39, 40, 41, 42, 43, 44, 45, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 59, 61, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 75, 76, 77, 78, 79, 80, 81
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OFFSET
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1,1
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COMMENTS
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The median of a multiset is either the middle part (for odd length), or the average of the two middle parts (for even length).
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LINKS
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EXAMPLE
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The terms together with their prime factors begin:
2: {2}
3: {3}
4: {2,2}
5: {5}
7: {7}
8: {2,2,2}
9: {3,3}
11: {11}
12: {2,2,3}
13: {13}
15: {3,5}
16: {2,2,2,2}
17: {17}
18: {2,3,3}
19: {19}
20: {2,2,5}
21: {3,7}
23: {23}
24: {2,2,2,3}
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MATHEMATICA
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Select[Range[2, 100], IntegerQ[Median[Flatten[ConstantArray@@@FactorInteger[#]]]]&]
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CROSSREFS
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Prime factors are listed by A027746.
For mean instead of median we have A078175, for prime indices A316413.
For prime indices instead of factors we have A359908, counted by A325347.
Positions of even terms in A360005.
A067340 lists numbers whose prime signature has integer mean.
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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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