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A098025 p and 2p-1 are both Pythagorean primes, i.e., congruent to 1 (mod 4). 2

%I

%S 37,97,157,229,337,577,601,661,829,877,937,997,1009,1069,1237,1297,

%T 1429,1609,1657,2029,2089,2137,2221,2281,2557,2617,3037,3061,3109,

%U 3169,3181,3529,3697,3709,3769,3877,4177,4261,4357,4621,4801,4861,4909,5557,5581

%N p and 2p-1 are both Pythagorean primes, i.e., congruent to 1 (mod 4).

%C The product p*(2p-1) generates a family of base-2 pseudoprimes (i.e., a subsequence of A001567).

%D J.-M. De Koninck and A.Mercier, 1001 Problèmes en Théorie Classique Des Nombres, Problème 878 pp. 108; 353, Ellipses Paris 2004.

%H Amiram Eldar, <a href="/A098025/b098025.txt">Table of n, a(n) for n = 1..10000</a>

%t Select[ Prime[ Range[1000]], Mod[#,4] == 1 && PrimeQ[2 #-1] && Mod[2 #-1,4] == 1 & ] (* _Jean-François Alcover_, Sep 14 2011 *)

%Y Cf. A001567, A002144, A005382.

%K nonn

%O 1,1

%A _Lekraj Beedassy_, Sep 10 2004

%E More terms from _Ray Chandler_, Sep 16 2004

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Last modified August 11 07:11 EDT 2022. Contains 356046 sequences. (Running on oeis4.)