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 A014946 Numbers n such that n divides 6^n-1. 12
 1, 5, 25, 125, 625, 1555, 3125, 7775, 15625, 38875, 78125, 194375, 390625, 483605, 971875, 1953125, 2418025, 4859375, 9673655, 9765625, 12090125, 24296875, 48368275, 48828125, 60450625, 120909025, 121484375, 150401155, 241841375 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Includes all powers of 5. If a term such as 1555 = 5*311 occurs, so does any number of the form 5^a * 311^b for a>3. Contribution from Alexander Adamchuk, May 16 2010: (Start) All terms that are not the powers of 5 are divisible by 5 and 311. Prime divisors of a(n) are {5, 311, 6221 , 15551, 155501, ...}. (End) LINKS MATHEMATICA Select[ Range[ 5*10^7], PowerMod[6, #, # ] == 1 & ] PROG (PARI) is(n)=Mod(6, n)^n==1 \\ Charles R Greathouse IV, Nov 04 2016 CROSSREFS Sequence in context: A250357 A216125 A057831 * A188580 A132839 A206451 Adjacent sequences:  A014943 A014944 A014945 * A014947 A014948 A014949 KEYWORD nonn AUTHOR EXTENSIONS Better description from Benoit Cloitre, Mar 06 2002 Edited and extended by Robert G. Wilson v, Jun 18 2002 a(25)-a(45) from Alexander Adamchuk, May 16 2010 STATUS approved

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Last modified November 15 04:00 EST 2018. Contains 317225 sequences. (Running on oeis4.)