A339653 a(n) is 0 if the smallest base-n Wieferich prime is < n, 1 if it is > n and 2 if no base-n Wieferich prime exists.

1, 1, 1, 0, 1, 0, 0, 0, 0, 1, 1, 0, 1, 1, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0

Offset

2

Comments

The value of a(47) is unknown since no base-47 Wieferich prime is known (cf. Fischer).

Links

Table of n, a(n) for n=2..33.

Richard Fischer, Thema: Fermatquotient B^(P-1) == 1 (mod P^2)

Example

For n = 5: The smallest base-5 Wieferich prime is 2 and 2 < 5 so a(5) = 0.

Prog

(PARI) a(n, bound) = forprime(p=1, bound, if(Mod(n, p^2)^(p-1)==1, if(p < n, return(0), return(1)))); ("bound reached")
for(n=2, 50, print1(a(n, 1e8), ", ")) \\ Execute the function like this to search the bases to 10^8

Crossrefs

Cf. A039951.

Sequence in context: A113431 A116915 A266178 * A255738 A296209 A076141

Adjacent sequences: A339650 A339651 A339652 * A339654 A339655 A339656

Keyword

nonn,hard,more

Author

Felix Fröhlich, Dec 12 2020

Status

approved