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 A082071 Smallest common prime-divisor of phi(n) = A000010(n) and sigma_2(n) = A001157(n); a(n)=1 if no common prime-divisor was found. 6
 1, 1, 2, 1, 2, 2, 2, 1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 5, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 1, 2, 2, 2, 2, 2 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS Antti Karttunen, Table of n, a(n) for n = 1..16384 FORMULA a(n) = A020639(gcd(A000010(n), A001157(n))). - Antti Karttunen, Nov 03 2017 MATHEMATICA Array[If[CoprimeQ[#1, #2], 1, Min@ Apply[Intersection, Map[FactorInteger[#][[All, 1]] &, {#1, #2}]]] & @@ {EulerPhi@ #, DivisorSigma[2, #]} &, 105] (* Michael De Vlieger, Nov 03 2017 *) PROG (PARI) A020639(n) = if(1==n, n, vecmin(factor(n)[, 1])); A082071(n) = A020639(gcd(eulerphi(n), sigma(n, 2))); \\ Antti Karttunen, Nov 03 2017 CROSSREFS Cf. A000010, A001157, A020639. Cf. also A082065, A082067, A082068, A082069, A082070, A082072. Sequence in context: A281012 A304943 A248597 * A082065 A082070 A082902 Adjacent sequences:  A082068 A082069 A082070 * A082072 A082073 A082074 KEYWORD nonn AUTHOR Labos Elemer, Apr 07 2003 EXTENSIONS Values corrected by R. J. Mathar, Jul 09 2011 More terms from Antti Karttunen, Nov 03 2017 STATUS approved

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Last modified January 28 12:58 EST 2020. Contains 331321 sequences. (Running on oeis4.)