A082063 Greatest common prime divisor of n and sigma_2(n) = A001157(n), or 1 if the two are relatively prime.

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

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: A169951 A174453 A361781 * 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