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A076358
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a(n) = numerator(n!/phi(n!)).
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2
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1, 2, 3, 3, 15, 15, 35, 35, 35, 35, 77, 77, 1001, 1001, 1001, 1001, 17017, 17017, 323323, 323323, 323323, 323323, 676039, 676039, 676039, 676039, 676039, 676039, 2800733, 2800733, 86822723, 86822723, 86822723, 86822723, 86822723, 86822723
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OFFSET
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1,2
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COMMENTS
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Denominator of Product_{p<=n, p prime} (1 - 1/p). - Franz Vrabec, Jan 28 2014
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LINKS
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FORMULA
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MATHEMATICA
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Numerator[#/EulerPhi[#]]&/@(Range[40]!) (* Harvey P. Dale, Apr 16 2016 *)
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PROG
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(PARI) a(n) = denominator(prod(p=1, n, if (isprime(p), (1-1/p), 1))); \\ Michel Marcus, Jan 28 2014
(PARI) first(n) = {my(res = vector(n), q = 2); res[1] = 1; res[2] = 1/2; forprime(p = 3, n, for(k = q + 1, p - 1, res[k] = res[k-1] ); res[p] = res[p-1]*(1-1/p); q = p; ); for(k = precprime(n)+1, n, res[k] = res[k-1] ); vector(n, i, denominator(res[i])) } \\ David A. Corneth, May 22 2020
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CROSSREFS
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KEYWORD
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easy,nonn,frac
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AUTHOR
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STATUS
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approved
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