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A273786
Numbers n where a prime p < n exists such that n^(p-1) == 1 (mod p^2), i.e., such that p is a base-n Wieferich prime.
3
5, 7, 8, 9, 10, 13, 17, 18, 19, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 35, 37, 38, 40, 41, 42, 43, 44, 45, 46, 48, 49, 50, 51, 53, 54, 55, 57, 60, 61, 62, 63, 64, 65, 67, 68, 69, 70, 71, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 85, 89, 91, 93, 94
OFFSET
1,1
COMMENTS
Numbers n such that A255920(n) > 0.
Complement of A255921. - Felix Fröhlich, Dec 03 2020
LINKS
EXAMPLE
The prime 5 satisfies 24^(5-1) == 1 (mod 5^2) and 5 < 24, so 24 is a term of the sequence.
MATHEMATICA
Select[Range@ 94, Function[n, Count[Prime@ Range@ PrimePi@ n, p_ /; Mod[n^(p - 1), p^2] == 1] > 0]] (* Michael De Vlieger, May 30 2016 *)
PROG
(PARI) is(n) = forprime(p=1, n-1, if(Mod(n, p^2)^(p-1)==1, return(1))); 0
CROSSREFS
KEYWORD
nonn
AUTHOR
Felix Fröhlich, May 30 2016
STATUS
approved