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 A114245 Number of Fermat pseudoprimes to base 3 less than 10^n. 7
 0, 1, 6, 23, 78, 246, 760, 2155, 5804, 15472, 39871, 102839 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS Table of n, a(n) for n=1..12. Eric Weisstein's World of Mathematics, Fermat Pseudoprime Index entries for sequences related to pseudoprimes FORMULA A005935(a(n)) < 10^n; A005935(a(n)+1) > 10^n. - R. J. Mathar, Feb 10 2007 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 Cf. A005935, A114247, A114249. Sequence in context: A058751 A034359 A220148 * A220238 A078798 A027043 Adjacent sequences: A114242 A114243 A114244 * A114246 A114247 A114248 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 STATUS approved

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Last modified September 23 19:57 EDT 2023. Contains 365554 sequences. (Running on oeis4.)