The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.



Thanks to everyone who made a donation during our annual appeal!
To see the list of donors, or make a donation, see the OEIS Foundation home page.

(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A178813 (Prime(n)^(p-1) - 1)/p^2 mod p, where p is the first prime that divides (prime(n)^(p-1) - 1)/p. 2


%S 487,4,1,1,46,1,0,1,11,1,2,1,0,2

%N (Prime(n)^(p-1) - 1)/p^2 mod p, where p is the first prime that divides (prime(n)^(p-1) - 1)/p.

%C (Prime(n)^(p-1) - 1)/p^2 mod p, where p = A174422(n) is the first Wieferich prime base prime(n).

%C (Prime(n)^(p-1) - 1)/p^2 mod p, where p is the first prime such that p^2 divides prime(n)^(p-1) - 1.

%C See references and additional comments, links, and cross-refs in A001220 and A039951.

%H Wikipedia, <a href="http://en.wikipedia.org/wiki/Fermat_quotient#Generalized_Wieferich_primes">Generalized Wieferich primes</a>

%F a(n) = k mod 2, if prime(n) = 4k+1.

%F a(n) = A178814(prime(n)) .

%F a(1) = A178812(1).

%e Prime(2) = 3 and the first prime p that divides (3^(p-1) - 1)/p is 11, so a(2) = (3^10 - 1)/11^2 mod 11 = 488 mod 11 = 4.

%Y Cf. A001220, A039951, A174422, A178812, A178814.

%K hard,more,nonn

%O 1,1

%A _Jonathan Sondow_, Jun 17 2010

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified January 18 05:09 EST 2020. Contains 330995 sequences. (Running on oeis4.)