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A114246
Number of Fermat pseudoprimes to bases 2 and 3 less than 10^n.
4
0, 0, 0, 7, 23, 66, 187, 485, 1272, 3270, 8139, 20015, 50090, 125284, 318729, 813380, 2104139, 5514763, 14627441
OFFSET
1,4
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
Cf. A052155.
Sequence in context: A266801 A066187 A259214 * A297315 A048457 A048458
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