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A082067 Smallest prime that divides n and phi(n)=A000010(n), or 1 if n and phi(n) are relatively prime. 7
1, 1, 1, 2, 1, 2, 1, 2, 3, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 3, 2, 1, 2, 5, 2, 3, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 3, 2, 1, 2, 1, 2, 3, 2, 1, 2, 7, 2, 1, 2, 1, 2, 5, 2, 3, 2, 1, 2, 1, 2, 3, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 5, 2, 1, 2, 1, 2, 3, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 3, 2, 1, 2, 1, 2, 3, 2, 1, 2, 1, 2, 3 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..16384

FORMULA

a(n) = A020639(A009195(n)). - Antti Karttunen, Nov 03 2017

MATHEMATICA

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_] := n; f2[x_] := EulerPhi[x]; Table[Min[Intersection[ba[f1[w]], ba[f2[w]]]], {w, 1, 128}]

(* Second program: *)

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

PROG

(PARI)

A020639(n) = if(1==n, n, vecmin(factor(n)[, 1]));

A082067(n) = A020639(gcd(eulerphi(n), n)); \\ Antti Karttunen, Nov 03 2017

CROSSREFS

Cf. A000010, A009195.

Cf. also A082061, A082068, A082069, A082070, A082071, A082072.

Sequence in context: A094076 A089611 A248470 * A082061 A327979 A107286

Adjacent sequences:  A082064 A082065 A082066 * A082068 A082069 A082070

KEYWORD

nonn

AUTHOR

Labos Elemer, Apr 07 2003

EXTENSIONS

Name clarified by Antti Karttunen, Nov 03 2017

STATUS

approved

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Last modified February 24 13:05 EST 2020. Contains 332209 sequences. (Running on oeis4.)