A339533 Numbers b > 1 such that the smallest four primes, i.e., 2, 3, 5 and 7 are base-b Wieferich primes.

557, 901, 1549, 2449, 4049, 5293, 5849, 6193, 7057, 7957, 8801, 9701, 12349, 13249, 14093, 14993, 15857, 16201, 16757, 18001, 19601, 20501, 21149, 21493, 22049, 23257, 23293, 24893, 25057, 25793, 26657, 27557, 28549, 30349, 31949, 32849, 33301, 34201, 35801

Offset: 1

Author

Felix Fröhlich, Dec 08 2020

Keywords

• nonn

Crossrefs

Cf. A256236. Row 1 of A319061.

Cf. smallest k primes are base-b Wieferich primes: A339531 (k=2), A339532 (k=3), A339534 (k=5), A339535 (k=6), A339536 (k=7), A339537 (k=8).

Programs

Mathematica

Select[Range[2, 36000], Function[b, AllTrue[{2, 3, 5, 7}, PowerMod[b, (# - 1), #^2] == 1 &]]] (* Michael De Vlieger, Dec 10 2020 *)

PARI

is(n) = forprime(p=1, 7, if(Mod(n, p^2)^(p-1)!=1, return(0))); 1