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A070251
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Unrelated-factorial numbers: product of numbers unrelated to n (numbers which have a common divisor with n but do not divide n).
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2
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1, 1, 1, 1, 1, 4, 1, 6, 6, 192, 1, 720, 1, 23040, 6480, 10080, 1, 12902400, 1, 34836480, 2449440, 1857945600, 1, 50295168000, 3000, 980995276800, 9797760, 9564703948800, 1, 1518492398911488000, 1, 41845579776000, 1571364748800
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OFFSET
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1,6
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COMMENTS
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a(p) = 1 if p is a prime. 4 is the only composite number such that a(4) = 1.
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LINKS
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FORMULA
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MAPLE
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remove(k->igcd(n, k)=1, {$1..n}); numtheory[divisors](n);
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MATHEMATICA
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a[n_] := Times @@ Complement[Range[n], Divisors[n]]/Times @@ Select[ Range[n], CoprimeQ[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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EXTENSIONS
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STATUS
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approved
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