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A173751
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a(n) = gcd(n, lcm_{p is a prime divisor of n} (p-1)) = gcd(n, A173614(n)).
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1
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1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 2, 1, 2, 1, 1, 1, 2, 1, 4, 3, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 1, 1, 2, 1, 2, 1, 2, 3, 4, 1, 6, 1, 2, 1, 2, 1, 2, 1, 2, 1, 4, 1, 2, 5, 2, 3, 2, 1, 4, 1, 2, 3, 1, 1, 2, 1, 4, 1, 2, 1, 2, 1, 2, 1, 2, 1, 6, 1, 4, 1, 2, 1, 6, 1, 2, 1, 2, 1, 2, 1, 2, 3, 2, 1, 2, 1, 2, 1, 4, 1, 2, 1, 4, 3
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OFFSET
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1,6
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COMMENTS
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LINKS
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EXAMPLE
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84 = 2^2*3*7; lcm{p-1|p is prime and divisor of 84} = lcm{1,2,6} = 6; gcd(84,6) = 6 ==> a(84)=6.
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MATHEMATICA
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fa=FactorInteger; lcm[n_] := Module[{aux = 1, lon = Length[fa[n]]}, Do[aux = LCM[aux, (fa[n][[i]][[1]] - 1)], {i, lon}]; aux] a[n_] := GCD[lcm[n], n]; Table[a[n], {n, 1, 300}]
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PROG
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(PARI) a(n)=gcd(n, lcm(apply(p->p-1, factor(n)[, 1]))) \\ Andrew Howroyd, Aug 06 2018
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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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