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A127092 Numbers n such that n^2 divides 11^n-1. 27
1, 2, 4, 5, 6, 10, 12, 20, 30, 42, 60, 84, 114, 156, 210, 222, 228, 244, 420, 444, 570, 732, 780, 798, 930, 1092, 1110, 1140, 1220, 1554, 1596, 1806, 1860, 2220, 2436, 2964, 3108, 3612, 3660, 3990, 4218, 5124, 5460, 5772, 6510, 7770, 7980, 8268, 8436, 9030 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(n) is a subset of A068383(n) = {1, 2, 4, 5, 6, 8, 10, 12, 16, 18, 20, 24, 25, 30, 32, 36, 40, 42, ...} Numbers n such that n divides 11^n-1.

LINKS

Table of n, a(n) for n=1..50.

MATHEMATICA

Select[Range[15000], IntegerQ[(PowerMod[11, #, #^2 ]-1)/#^2 ]&]

Join[{1}, Select[Range[9100], PowerMod[11, #, #^2]==1&]] (* Harvey P. Dale, Dec 30 2018 *)

CROSSREFS

Cf. A127100, A127101, A127102, A127104, A123105, A127106, A127107. Cf. A068383 = numbers n such that n divides 11^n-1.

Sequence in context: A162534 A233193 A177911 * A128171 A233768 A240748

Adjacent sequences:  A127089 A127090 A127091 * A127093 A127094 A127095

KEYWORD

nonn

AUTHOR

Alexander Adamchuk, Jan 05 2007

STATUS

approved

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Last modified June 26 00:41 EDT 2019. Contains 324367 sequences. (Running on oeis4.)