OFFSET
1,4
LINKS
Eric Weisstein's World of Mathematics, Fermat Pseudoprime.
MATHEMATICA
Table[Count[Select[Range[2, 10^6], ! PrimeQ[#] && PowerMod[2, # - 1, #] == 1 && PowerMod[3, # - 1, #] == 1 &], x_ /; x < 10^n], {n, 6}] (* Robert Price, Jun 09 2019 *)
PROG
(PARI) my(n=1, i=0); forcomposite(k=1, 1e20, if(Mod(2, k)^(k-1)==1 && Mod(3, k)^(k-1)==1, i++); if(k==10^n, print1(i, ", "); n++)) \\ Felix Fröhlich, Oct 11 2015
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Eric W. Weisstein, Nov 18 2005
EXTENSIONS
a(9) from Felix Fröhlich, Oct 11 2015
a(10)-a(11) from Amiram Eldar, Sep 18 2021
a(12)-a(19) from Amiram Eldar, Apr 22 2022
STATUS
approved