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A082063 Greatest common prime divisor of n and sigma_2(n) = A001157(n), or 1 if the two are relatively prime. 6
1, 1, 1, 1, 1, 2, 1, 1, 1, 5, 1, 3, 1, 2, 5, 1, 1, 1, 1, 2, 1, 2, 1, 2, 1, 2, 1, 7, 1, 5, 1, 1, 1, 2, 5, 3, 1, 2, 1, 5, 1, 2, 1, 2, 1, 2, 1, 2, 1, 5, 1, 2, 1, 2, 1, 2, 1, 2, 1, 5, 1, 2, 7, 1, 13, 2, 1, 2, 1, 5, 1, 1, 1, 2, 5, 2, 1, 2, 1, 2, 1, 2, 1, 7, 5, 2, 1, 2, 1, 5, 1, 2, 1, 2, 1, 3, 1, 1, 1, 1, 1, 2, 1, 2, 5 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,6

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = A006530(A179930(n)). - Antti Karttunen, Nov 03 2017

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[2, x]; Table[Max[Intersection[ba[f1[w]], ba[f2[w]]]], {w, 1, 128}]

(* Second program: *)

Array[If[CoprimeQ[#1, #2], 1, Max@ Apply[Intersection, Map[FactorInteger[#][[All, 1]] &, {#1, #2}]]] & @@ {#, DivisorSigma[2, #]} &, 105] (* Michael De Vlieger, Nov 03 2017 *)

PROG

(PARI)

A006530(n) = if(1==n, n, vecmax(factor(n)[, 1]));

A082063(n) = A006530(gcd(sigma(n, 2), n)); \\ Antti Karttunen, Nov 03 2017

CROSSREFS

Cf. A006530, A001157, A179930.

Cf. also A082061, A082062, A082064, A082065, A082066, A082069.

Sequence in context: A275422 A169951 A174453 * A260148 A327778 A099940

Adjacent sequences:  A082060 A082061 A082062 * A082064 A082065 A082066

KEYWORD

nonn

AUTHOR

Labos Elemer, Apr 07 2003

EXTENSIONS

Erroneous comment removed by Antti Karttunen, Nov 03 2017

STATUS

approved

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Last modified October 14 09:25 EDT 2019. Contains 327995 sequences. (Running on oeis4.)