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A166123
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If n is prime, a(n) = 1; otherwise, a(n) is gcd(n, d) where d is the denominator of the (n-1)-th Bernoulli number.
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1
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1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 5, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 15, 1, 1, 1, 7, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 5, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 5, 1, 3, 1, 1, 1, 7, 1, 3, 1, 1, 1, 1, 1, 3, 1
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OFFSET
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1,9
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LINKS
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FORMULA
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MATHEMATICA
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Table[If[PrimeQ[n], 1, GCD[n, Denominator[BernoulliB[n-1]]]], {n, 100}] (* Harvey P. Dale, Sep 07 2017 *)
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PROG
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(PARI) a(n)=my(b=bernfrac(n-1)); denominator(b)/denominator(b*n)/if(isprime(n), n, 1) \\ Charles R Greathouse IV, Jun 20 2011
(PARI) a(n)=if(isprime(n), 1, my(b=bernfrac(n-1)); denominator(b)/denominator(b*n)) \\ Charles R Greathouse IV, Jun 20 2011
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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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