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 A255924 Bases b for which exactly three Wieferich primes p with p < b exist such that p is a base-b Wieferich prime. 11
 19, 28, 53, 68, 80, 89, 107, 129, 137, 143, 145, 146, 147, 148, 170, 177, 181, 197, 215, 224, 253, 263, 268, 299, 307, 324, 332, 333, 334, 339, 341, 349, 350, 354, 357, 359, 360, 362, 368, 373, 377, 389, 393, 399, 402, 403, 410, 413, 437, 440, 449, 451, 457 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Numbers b such that A255920(b) = 3. LINKS Felix Fröhlich, Table of n, a(n) for n = 1..10000 Eric Weisstein's World of Mathematics, Wieferich Prime PROG (PARI) is(n) = my(i=0); forprime(p=1, n-1, if(Mod(n, p^2)^(p-1)==1, i++); if(i > 3, return(0))); i==3 (Sage) [b for b in range(3, 458) if len([p for p in range(2, b) if is_prime(p) and mod(b, p^2)^(p-1)==1])==3] # Danny Rorabaugh, Mar 31 2015 CROSSREFS Cf. A255920. Cf. bases b with exactly k base-b Wieferich primes less than b: A255921 (k=0), A255922 (k=1), A255923 (k=2), A255925 (k=4), A325881 (k=5), A325882 (k=6), A325883 (k=7), A325884 (k=8), A325885 (k=9), A325886 (k=10). Sequence in context: A369341 A368871 A120144 * A067452 A123944 A095046 Adjacent sequences: A255921 A255922 A255923 * A255925 A255926 A255927 KEYWORD nonn AUTHOR Felix Fröhlich, Mar 23 2015 STATUS approved

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Last modified August 11 23:09 EDT 2024. Contains 375079 sequences. (Running on oeis4.)