OFFSET
1,3
LINKS
Michal Mikuš, Computing the Pseudoprimes up to 10^13, Cybernetics and Informatics, International Conference SSKI, February 10-13, 2010.
Eric Weisstein's World of Mathematics, Fermat Pseudoprime.
FORMULA
MATHEMATICA
Table[Count[Select[Range[2, 10^6], ! PrimeQ[#] && PowerMod[3, # - 1, #] == 1 &], x_ /; x < 10^n], {n, 6}] (* Robert Price, Jun 09 2019 *)
PROG
(PARI) isFps(n, b)= { if(isprime(n), return(0) ) ; if( (b^(n-1)) % n == 1, return(1), return(0) ) ; } { a=0 ; e=1 ; for(n=1, 10^12, if( n == 10^e, e++ ; print(a) ; ) ; a += isFps(n, 3) ; ) ; } \\ R. J. Mathar, Feb 10 2007
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Eric W. Weisstein, Nov 18 2005
EXTENSIONS
a(9)-a(10) from Washington Bomfim, Mar 02 2012
a(11)-a(12) from Hiroaki Yamanouchi, Sep 25 2015
a(13) from Mikuš (2010) added by Amiram Eldar, Mar 31 2024
STATUS
approved