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A163644
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Product of primes which do not exceed n and do not divide the swinging factorial n$ (A056040).
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1
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1, 1, 1, 1, 1, 1, 3, 3, 3, 1, 5, 5, 5, 5, 35, 7, 7, 7, 21, 21, 105, 5, 55, 55, 165, 33, 429, 143, 1001, 1001, 1001, 1001, 1001, 91, 1547, 221, 221, 221, 4199, 323, 323, 323, 2261, 2261, 24871, 24871, 572033, 572033, 572033, 81719, 408595, 24035, 312455
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OFFSET
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0,7
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COMMENTS
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LINKS
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EXAMPLE
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a(20) = 105 because in the prime-factorization of 20$ the primes 3, 5 and 7 are missing and 3*5*7 = 105.
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MAPLE
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a := proc(n) local p; mul(p, p=select(isprime, {$1..n})
minus numtheory[factorset](n!/iquo(n, 2)!^2)) end:
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MATHEMATICA
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A034386[x_] := Apply[Times, Table[Prime[w], {w, 1, PrimePi[x]}]];
sf[n_] := With[{f = Floor[n/2]}, Pochhammer[f + 1, n - f]/f!];
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CROSSREFS
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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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