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 A253684 Primes q with A253683(n) > q > A253685(n) such that (A253683(n), q, A253685(n)) forms a Wieferich triple. 3
 11, 23, 5, 1667, 73, 821, 18043, 2393, 20771, 2251, 1006003 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS In analogy to a Wieferich pair, a set of three primes p, q, r can be called a 'Wieferich triple' if its members satisfy either of the following two sets of congruences: p^(q-1) == 1 (mod q^2), q^(r-1) == 1 (mod r^2), r^(p-1) == 1 (mod p^2) p^(r-1) == 1 (mod r^2), r^(q-1) == 1 (mod q^2), q^(p-1) == 1 (mod p^2) a(9) must have A253683(n) > 121637. - Felix Fröhlich, Jun 18 2016 a(12) must have A253683(n) > 5*10^6. - Giovanni Resta, Jun 20 2016 LINKS Wikipedia, Wieferich pair PROG (PARI) forprime(p=1, , forprime(q=1, p, forprime(r=1, q, if((Mod(p, q^2)^(q-1)==1 && Mod(q, r^2)^(r-1)==1 && Mod(r, p^2)^(p-1)==1) || (Mod(p, r^2)^(r-1)==1 && Mod(r, q^2)^(q-1)==1 && Mod(q, p^2)^(p-1)==1), print1(q, ", "))))) CROSSREFS Cf. A124121, A124122. Cf. A253683, A253685. Sequence in context: A118133 A225186 A155973 * A180481 A110044 A032663 Adjacent sequences:  A253681 A253682 A253683 * A253685 A253686 A253687 KEYWORD nonn,hard,more AUTHOR Felix Fröhlich, Jan 09 2015 EXTENSIONS a(8) from Felix Fröhlich, Jun 18 2016 Name edited by Felix Fröhlich, Jun 18 2016 a(9)-a(11) from Giovanni Resta, Jun 20 2016 STATUS approved

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Last modified August 15 12:33 EDT 2020. Contains 336499 sequences. (Running on oeis4.)