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A082062 Greatest common prime-divisor of n and sigma(n)=A000203(n); a(n)=1 if no common prime-divisor was found. 7
1, 1, 1, 1, 1, 3, 1, 1, 1, 2, 1, 2, 1, 2, 3, 1, 1, 3, 1, 2, 1, 2, 1, 3, 1, 2, 1, 7, 1, 3, 1, 1, 3, 2, 1, 1, 1, 2, 1, 5, 1, 3, 1, 2, 3, 2, 1, 2, 1, 1, 3, 2, 1, 3, 1, 2, 1, 2, 1, 3, 1, 2, 1, 1, 1, 3, 1, 2, 3, 2, 1, 3, 1, 2, 1, 2, 1, 3, 1, 2, 1, 2, 1, 7, 1, 2, 3, 2, 1, 3, 7, 2, 1, 2, 5, 3, 1, 1, 3, 1, 1, 3, 1, 2, 3 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,6

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

MATHEMATICA

"factors/exponent SET "; ffi[x_] := Flatten[FactorInteger[x]] lf[x_] := Length[FactorInteger[x]] ba[x_] := Table[Part[ffi[x], 2*w-1], {w, 1, lf[x]}] f1[x_] := x; f2[x_] := DivisorSigma[1, x] Table[Max[Intersection[ba[f1[w]], ba[f2[w]]]], {w, 1, 128}]

PROG

(PARI) gpf(n)=if(n>1, my(f=factor(n)[, 1]); f[#f], 1)

a(n)=gpf(gcd(sigma(n), n)) \\ Charles R Greathouse IV, Feb 19 2013

CROSSREFS

Cf. A009194, A006530, A000203, A082061-A082065; A192795.

Sequence in context: A298667 A226166 A209155 * A030370 A100808 A010277

Adjacent sequences:  A082059 A082060 A082061 * A082063 A082064 A082065

KEYWORD

nonn

AUTHOR

Labos Elemer, Apr 07 2003

STATUS

approved

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Last modified February 26 21:58 EST 2020. Contains 332295 sequences. (Running on oeis4.)