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A325392
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Number of permutations of the multiset of prime factors of n whose first part is not 2.
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3
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1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 2, 0, 1, 2, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 4, 1, 0, 2, 1, 2, 3, 1, 1, 2, 1, 1, 4, 1, 1, 3, 1, 1, 1, 1, 2, 2, 1, 1, 3, 2, 1, 2, 1, 1, 6, 1, 1, 3, 0, 2, 4, 1, 1, 2, 4, 1, 4, 1, 1, 3, 1, 2, 4, 1, 1, 1, 1, 1, 6, 2, 1, 2, 1, 1, 9, 2, 1, 2, 1, 2, 1, 1, 2, 3, 3, 1, 4, 1, 1, 6
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OFFSET
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1,15
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LINKS
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FORMULA
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EXAMPLE
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The a(90) = 9 permutations of {2,3,3,5} not starting with 2:
3 2 3 5
3 2 5 3
3 3 2 5
3 3 5 2
3 5 2 3
3 5 3 2
5 2 3 3
5 3 2 3
5 3 3 2
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MATHEMATICA
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primeMS[n_]:=If[n==1, {}, Flatten[Cases[FactorInteger[n], {p_, k_}:>Table[PrimePi[p], {k}]]]];
Table[Length[Select[Permutations[primeMS[n]], #=={}||First[#]>1&]], {n, 100}]
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PROG
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(PARI)
A008480(n) = {my(sig=factor(n)[, 2]); vecsum(sig)!/factorback(apply(k->k!, sig))}; \\ From code in A008480
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CROSSREFS
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Number of times n appears in A325390.
Cf. A008480, A056239, A112798, A325327, A325362, A325364, A325367, A325403 (even bisection), A325407, A325460, A325461.
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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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