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A316786
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Denominator of an upper bound for the maximal element in phi^(-1)(n).
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2
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1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 8, 1, 1, 1, 4, 1, 2, 1, 2, 1, 1, 1, 4, 1, 1, 1, 4, 1, 20, 1, 2, 1, 1, 1, 1728, 1, 1, 1, 8, 1, 2, 1, 2, 1, 1, 1, 32, 1, 1, 1, 4, 1, 2, 1, 2, 1, 1, 1, 5760, 1, 1, 1, 1, 1, 44, 1, 1, 1, 10, 1, 62208, 1, 1, 1, 1, 1, 2, 1, 64, 1, 1, 1, 192, 1, 1, 1, 88, 1, 120, 1, 2, 1, 1, 1, 1536, 1, 1, 1, 8
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OFFSET
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1,12
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COMMENTS
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LINKS
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FORMULA
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Denominator of n*Product_{p prime, (p-1)|n} p/(p-1).
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EXAMPLE
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For n = 12, there are 5 primes p with (p-1)|12: p1 = 2, p2 = 3, p3 = 5, p4 = 7, and p5 = 13. The denominator of 12*(2/1)*(3/2)*(5/4)*(7/6)*(13/12) = 455/8 is a(12) = 8.
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MAPLE
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with(numtheory): A316786 := proc(n) local d, N; N:=n; for d in divisors(n) do if is prime(d+1) then N := (N*(d+1))/(d) end if; end do; denom(N); end proc;
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PROG
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(PARI) a(n) = my(p=n); fordiv(n, d, if (isprime(d+1), p *= (d+1)/d)); denominator(p); \\ Michel Marcus, Jul 29 2018
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CROSSREFS
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KEYWORD
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nonn,frac
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AUTHOR
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STATUS
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approved
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