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A361201
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Product of the right half (exclusive) of the multiset of prime factors of n; a(1) = 0.
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17
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0, 1, 1, 2, 1, 3, 1, 2, 3, 5, 1, 3, 1, 7, 5, 4, 1, 3, 1, 5, 7, 11, 1, 6, 5, 13, 3, 7, 1, 5, 1, 4, 11, 17, 7, 9, 1, 19, 13, 10, 1, 7, 1, 11, 5, 23, 1, 6, 7, 5, 17, 13, 1, 9, 11, 14, 19, 29, 1, 15, 1, 31, 7, 8, 13, 11, 1, 17, 23, 7, 1, 9, 1, 37, 5, 19, 11, 13, 1
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OFFSET
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1,4
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LINKS
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FORMULA
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EXAMPLE
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The prime factors of 250 are {2,5,5,5}, with right half (exclusive) {5,5}, with product 25, so a(250) = 25.
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MATHEMATICA
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Table[If[n==1, 0, Times@@Take[Join@@ConstantArray@@@FactorInteger[n], -Floor[PrimeOmega[n]/2]]], {n, 100}]
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CROSSREFS
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Positions of first appearances are A123666.
The left inclusive version A347043.
A001221 counts distinct prime factors.
A006530 gives greatest prime factor.
First for prime indices, second for partitions, third for prime factors:
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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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