A114245 Number of Fermat pseudoprimes to base 3 less than 10^n.
0, 1, 6, 23, 78, 246, 760, 2155, 5804, 15472, 39871, 102839, 264461
Offset: 1
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.
- Index entries for sequences related to pseudoprimes.
Programs
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Mathematica
Table[Count[Select[Range[2, 10^6], ! PrimeQ[#] && PowerMod[3, # - 1, #] == 1 &], x_ /; x < 10^n], {n, 6}] (* Robert Price, Jun 09 2019 *) -
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
Formula
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