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%I #11 Aug 28 2019 09:46:52
%S 1565891838737,1985917919077,2060476510097,5590084720897,
%T 39623323626437,94860314619877,114027286862737,115071875848337,
%U 117140013119377,136739205150917,246382184192357,254109295929637,265883157493777,340055949647237,378534223873937
%N Primes p of the form 4m^2+1 such that q=4p^2+1, r=4q^2+1 and s=4r^2+1 are all prime.
%C Corresponding values of k: 625678,704613,717718,1182168,3147353,4869813,5339178,5363578,5411562,5846777,7848283,7970403,8152962,9220303,9727978.
%t apQ[p_]:=Module[{q=4p^2+1,r},r=4q^2+1;AllTrue[{p,q,r,4r^2+1},PrimeQ]]; Select[ 4*Range[ 10^7]^2+1,apQ] (* The program uses the AllTrue function from Mathematica version 10 *) (* _Harvey P. Dale_, Aug 28 2019 *)
%Y Subsequence of A248887. Cf. A001912, A121326, A121834, A248887.
%K nonn
%O 1,1
%A _Zak Seidov_, Mar 05 2015