

A255885


Smallest base b such that there exist exactly n Wieferich pseudoprimes (composites c satisfying b^(c1) == 1 (mod c^2)) less than b.


5



17, 65, 145, 485, 649, 1297, 577, 2024, 5185, 8182, 7057, 8749, 14401, 30753, 56449, 57601, 77401, 129473, 51841, 129601, 254017, 296449, 202501, 389377
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OFFSET

1,1


LINKS

Table of n, a(n) for n=1..24.


PROG

(PARI) for(n=1, 10, b=2; while(b > 0, i=0; forcomposite(c=2, b, if(Mod(b, c^2)^(c1)==1, i++)); if(i==n, print1(b, ", "); break({1})); b++))
(Python)
from itertools import count
from sympy import isprime
def A255885(n):
for b in count(1):
if n == sum(1 for c in range(2, b+1) if not isprime(c) and pow(b, c1, c**2) == 1):
return b # Chai Wah Wu, May 18 2022


CROSSREFS

Cf. A244752, A252232, A255901.
Sequence in context: A086533 A226685 A108211 * A130885 A036545 A146807
Adjacent sequences: A255882 A255883 A255884 * A255886 A255887 A255888


KEYWORD

nonn,more


AUTHOR

Felix Fröhlich, Mar 09 2015


EXTENSIONS

a(20) from Chai Wah Wu, May 18 2022
a(21)a(24) from Chai Wah Wu, May 19 2022


STATUS

approved



