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A054991
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Number of prime divisors of n! - 1 (counted with multiplicity).
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14
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0, 0, 1, 1, 2, 1, 1, 2, 3, 2, 4, 1, 2, 1, 5, 2, 3, 3, 3, 2, 4, 3, 2, 2, 3, 2, 2, 4, 5, 1, 3, 1, 1, 2, 3, 2, 5, 1, 4, 2, 4, 4, 7, 4, 5, 5, 2, 4, 3, 2, 5, 5, 4, 6, 6, 5, 6, 5, 2, 3, 4, 4, 5, 4, 6, 4, 7, 2, 6, 5, 5, 3, 4, 5, 7, 3, 5, 4, 2, 4, 4, 4, 4, 6, 2, 3, 4
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OFFSET
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1,5
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COMMENTS
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The series is related to the product of primes and the "proof" of the existence of infinite many prime twins.
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LINKS
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EXAMPLE
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a(2)=0 because 2! - 1 = 1 (and this is not a prime number) a(5)=2 because 5! -1 = 119 = 7 * 17
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MATHEMATICA
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a[q_] := Module[{x, n}, x=FactorInteger[q!-1]; n=Length[x]; Sum[Table[x[[i]][[2]], {i, n}][[j]], {j, n}]]
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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Arne Ring (arne.ring(AT)epost.de), May 30 2000
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EXTENSIONS
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STATUS
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approved
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