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A124676 a(n) = largest integer < n such that the positive integers <= a(n) and coprime to a(n) are also coprime to n. 0
1, 2, 2, 4, 2, 6, 6, 6, 4, 10, 6, 12, 6, 3, 14, 16, 12, 18, 10, 6, 10, 22, 18, 20, 12, 24, 14, 28, 2, 30, 30, 9, 16, 5, 30, 36, 18, 12, 30, 40, 6, 42, 22, 30, 22, 46, 42, 42, 40, 15, 26, 52, 48, 10, 42, 18, 28, 58, 30, 60, 30, 42, 62, 10, 6, 66, 34, 21, 4, 70, 66, 72, 36, 60, 38, 7, 12 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,2

LINKS

Table of n, a(n) for n=2..78.

EXAMPLE

The positive integers k, k <= 6, where the positive integers <= k and coprime to k are also coprime to 6, are 1,2,6. So a(6) = the largest of these < 6, which is 2.

MATHEMATICA

f[n_] := Select[Range[n], GCD[ #, n] == 1 &]; g[n_] := Select[Range[n - 1], Times @@ GCD[f[ # ], n] == 1 &]; Max /@ Table[g[n], {n, 2, 80}] (* Ray Chandler, Dec 24 2006 *)

CROSSREFS

Cf. A126260, A073353.

Sequence in context: A078429 A358039 A171751 * A076249 A062170 A307536

Adjacent sequences: A124673 A124674 A124675 * A124677 A124678 A124679

KEYWORD

nonn

AUTHOR

Leroy Quet, Dec 24 2006

EXTENSIONS

Extended by Ray Chandler, Dec 24 2006

STATUS

approved

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Last modified December 5 02:30 EST 2022. Contains 358572 sequences. (Running on oeis4.)