login
Numbers b > 1 such that the smallest eight primes, i.e., 2, 3, 5, 7, 11, 13, 17 and 19 are base-b Wieferich primes.
6

%I #4 Dec 12 2020 06:17:32

%S 126664001,133487693,141313157,236176001,242883757,356977349,

%T 358254649,383691493

%N Numbers b > 1 such that the smallest eight primes, i.e., 2, 3, 5, 7, 11, 13, 17 and 19 are base-b Wieferich primes.

%o (PARI) is(n) = forprime(p=1, 19, if(Mod(n, p^2)^(p-1)!=1, return(0))); 1

%Y Cf. A256236. Row 1 of A319065.

%Y Cf. smallest k primes are base-b Wieferich primes: A339531 (k=2), A339532 (k=3), A339533 (k=4), A339534 (k=5), A339535 (k=6), A339536 (k=7).

%K nonn,more

%O 1,1

%A _Felix Fröhlich_, Dec 08 2020