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A336414
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Number of divisors of n! with distinct prime multiplicities.
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24
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1, 1, 2, 3, 7, 10, 20, 27, 48, 86, 147, 195, 311, 390, 595, 1031, 1459, 1791, 2637, 3134, 4747, 7312, 10766, 12633, 16785, 26377, 36142, 48931, 71144, 82591, 112308, 128023, 155523, 231049, 304326, 459203, 568095, 642446, 812245, 1137063, 1441067, 1612998, 2193307, 2429362
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OFFSET
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0,3
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COMMENTS
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A number has distinct prime multiplicities iff its prime signature is strict.
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LINKS
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FORMULA
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EXAMPLE
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The first and second columns below are the a(6) = 20 counted divisors of 6! together with their prime signatures. The third column shows the A000005(6!) - a(6) = 10 remaining divisors.
1: () 20: (2,1) | 6: (1,1)
2: (1) 24: (3,1) | 10: (1,1)
3: (1) 40: (3,1) | 15: (1,1)
4: (2) 45: (2,1) | 30: (1,1,1)
5: (1) 48: (4,1) | 36: (2,2)
8: (3) 72: (3,2) | 60: (2,1,1)
9: (2) 80: (4,1) | 90: (1,2,1)
12: (2,1) 144: (4,2) | 120: (3,1,1)
16: (4) 360: (3,2,1) | 180: (2,2,1)
18: (1,2) 720: (4,2,1) | 240: (4,1,1)
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MATHEMATICA
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Table[Length[Select[Divisors[n!], UnsameQ@@Last/@FactorInteger[#]&]], {n, 0, 15}]
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PROG
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(PARI) a(n) = sumdiv(n!, d, my(ex=factor(d)[, 2]); #vecsort(ex, , 8) == #ex); \\ Michel Marcus, Jul 24 2020
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CROSSREFS
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Numbers with distinct prime multiplicities are A130091.
Divisors with distinct prime multiplicities are counted by A181796.
The maximum divisor with distinct prime multiplicities is A327498.
Divisors of n! with equal prime multiplicities are counted by A336415.
Factorial numbers: A000142, A007489, A022559, A027423, A048656, A048742, A071626, A325272, A325273, A325617, A336416.
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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