A255922 Bases b for which exactly one Wieferich prime p with p < b exists such that p is a base-b Wieferich prime.

5, 7, 8, 9, 10, 13, 21, 22, 23, 24, 25, 27, 29, 30, 31, 32, 33, 35, 38, 42, 43, 44, 45, 46, 48, 50, 54, 55, 60, 61, 64, 70, 74, 77, 78, 79, 85, 91, 94, 98, 100, 105, 110, 112, 113, 115, 120, 122, 126, 128, 131, 132, 133, 136, 138, 141, 150, 151, 152, 153, 154

Offset: 1

Author

Felix Fröhlich, Mar 12 2015

Keywords

• nonn

Comments

Numbers b such that A255920(n) = 1.

Links

• Felix Fröhlich, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A255920.

Cf. bases b with exactly k base-b Wieferich primes less than b: A255921 (k=0), A255923 (k=2), A255924 (k=3), A255925 (k=4), A325881 (k=5), A325882 (k=6), A325883 (k=7), A325884 (k=8), A325885 (k=9), A325886 (k=10).

Programs

PARI

is(n) = my(i=0); forprime(p=1, n-1, if(Mod(n, p^2)^(p-1)==1, i++); if(i > 1, return(0))); i==1