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A083734 Pseudoprimes to bases 3 and 5. 2

%I #19 Jun 29 2019 08:32:41

%S 1541,1729,1891,2821,6601,8911,15841,29341,41041,46657,52633,63973,

%T 75361,88831,101101,112141,115921,126217,146611,162401,172081,188461,

%U 218791,252601,294409,314821,334153,340561,342271,399001,410041,416641

%N Pseudoprimes to bases 3 and 5.

%H Amiram Eldar, <a href="/A083734/b083734.txt">Table of n, a(n) for n = 1..15806</a> (terms 1..147 from R. J. Mathar)

%H F. Richman, <a href="http://math.fau.edu/Richman/carm.htm">Primality testing with Fermat's little theorem</a>

%F a(n) = n-th positive integer k(>1) such that 3^(k-1) = 1 (mod k) and 5^(k-1) = 1 (mod k).

%e a(1)=1541 since it is the first nonprime number such that 3^(k-1) = 1 (mod k) and 5^(k-1) = 1 (mod k). - clarified by _Harvey P. Dale_, Jan 29 2013

%t Select[Range[420000],!PrimeQ[#]&&PowerMod[3,#-1,#]==PowerMod[5,#-1,#]==1&] (* _Harvey P. Dale_, Jan 29 2013 *)

%Y Intersection of A005935 and A005936.

%K easy,nonn

%O 1,1

%A Serhat Sevki Dincer (sevki(AT)ug.bilkent.edu.tr), May 05 2003

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Last modified March 28 12:26 EDT 2024. Contains 371254 sequences. (Running on oeis4.)