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A083738 Pseudoprimes to bases 2,3 and 7. 1
1105, 2465, 10585, 18721, 29341, 46657, 75361, 104653, 115921, 162401, 226801, 252601, 278545, 294409, 314821, 334153, 340561, 399001, 410041, 449065, 488881, 512461, 530881, 534061, 552721, 574561, 658801, 721801, 852841, 1024651 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10460 (terms 1..98 from R. J. Mathar)

F. Richman, Primality testing with Fermat's little theorem

FORMULA

a(n) = n-th positive integer k(>1) such that 2^(k-1) = 1 (mod k), 3^(k-1) = 1 (mod k) and 7^(k-1) = 1 (mod k).

EXAMPLE

a(1)=1105 since it is the first number such that 2^(k-1) = 1 (mod k), 3^(k-1) = 1 (mod k) and 7^(k-1) = 1 (mod k).

MATHEMATICA

Select[Range[1, 10^5, 2], CompositeQ[#] &&  PowerMod[2, #-1, #] == PowerMod[3, #-1, #] == PowerMod[7, #-1, #] == 1&] (* Amiram Eldar, Jun 29 2019 *)

CROSSREFS

Intersection of A001567 and A083735. Intersection of A005935 and A083733. - R. J. Mathar, Apr 05 2011

Sequence in context: A264498 A102924 A214017 * A265237 A291602 A275881

Adjacent sequences:  A083735 A083736 A083737 * A083739 A083740 A083741

KEYWORD

easy,nonn

AUTHOR

Serhat Sevki Dincer (sevki(AT)ug.bilkent.edu.tr), May 05 2003

STATUS

approved

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Last modified February 20 13:10 EST 2020. Contains 332076 sequences. (Running on oeis4.)