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Pseudoprimes to base 2 of the form 4k+3.
3

%I #16 Oct 26 2015 22:20:22

%S 1387,2047,4371,8911,13747,14491,19951,42799,60787,90751,123251,

%T 150851,256999,258511,271951,272251,275887,294271,387731,396271,

%U 422659,435671,443719,452051,476971,514447,672487,680627,741751,769567,877099,916327,1024651,1052503,1092547,1152271,1277179,1302451,1325843,1397419,1419607,1433407,1441091,1459927

%N Pseudoprimes to base 2 of the form 4k+3.

%C In at least the first 1801533 values (that is, for 2-pseudoprimes <10^15) of A001567, the entries of the form 4k+3 are less numerous than those of the form 4k+1. Is this always the case?

%H Charles R Greathouse IV, <a href="/A177884/b177884.txt">Table of n, a(n) for n = 1..10000</a>

%F A001567 INTERSECT A004767.

%o (PARI) forstep(n=3,10^7,4,if(isprime(n),next());if(Mod(2,n)^(n-1)==1,print1(n,", ")))

%Y Cf. A001567, A178723.

%K nonn

%O 1,1

%A _Juri-Stepan Gerasimov_, Dec 14 2010

%E Terms corrected by _R. J. Mathar_, Dec 17 2010