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A091733 a(n) is the least m > 1 such that m^3 = 1 (mod n). 2
2, 3, 4, 5, 6, 7, 2, 9, 4, 11, 12, 13, 3, 9, 16, 17, 18, 7, 7, 21, 4, 23, 24, 25, 26, 3, 10, 9, 30, 31, 5, 33, 34, 35, 11, 13, 10, 7, 16, 41, 42, 25, 6, 45, 16, 47, 48, 49, 18, 51, 52, 9, 54, 19, 56, 9, 7, 59, 60, 61, 13, 5, 4, 65, 16, 67, 29, 69, 70, 11, 72, 25, 8, 47, 76, 45, 23, 55, 23 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(n) <= n + 1; the inequality is strict iff n is divisible by 9 or by a prime congruent to 1 mod 3. - Robert Israel, May 27 2014

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

EXAMPLE

a(7) = 2 because 2^3 is congruent to 1 (mod 7).

MAPLE

A:= n -> min(select(t -> type((t^3-1)/n, integer), [$2 .. n+1]));

map(A, [$1 .. 1000]); # Robert Israel, May 27 2014

MATHEMATICA

f[n_] := Block[{x = 2}, While[Mod[x^3 - 1, n] != 0, x++]; x]; Array[f, 79] (* Robert G. Wilson v, Mar 29 2016 *)

PROG

(MATLAB) m = 2; while mod(m^3 - 1, n); m = m + 1; end; m

(PARI) a(n) = my(k = 2); while(Mod(k, n)^3 != 1, k++); k; \\ Michel Marcus, Mar 30 2016

CROSSREFS

Cf. A070667, A076947, A083501.

Sequence in context: A173527 A043267 A167514 * A066990 A097449 A104415

Adjacent sequences:  A091730 A091731 A091732 * A091734 A091735 A091736

KEYWORD

easy,nonn

AUTHOR

David Wasserman, Mar 05 2004

STATUS

approved

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Last modified May 18 15:25 EDT 2021. Contains 343995 sequences. (Running on oeis4.)