This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A121834 #10 Nov 07 2016 17:40:22
%S A121834 5,37,677,1297,2917,8837,13457,50177,147457,156817,246017,341057,
%T A121834 414737,746497,1136357,1726597,1833317,2119937,2802277,2808977,
%U A121834 3013697,3549457,3865157,3896677,4104677,4384837,5354597,5410277,5779217,6031937,6635777,7001317
%N A121834 Primes p of the form 4*n^2 + 1 such that 4*p^2+1 is also prime.
%C A121834 Intersection of A001912 and A121326. Except for the first term all other terms are == 7 (mod 10). Also all the primes 4*p^2+1 are == 7 (mod 10). - _Zak Seidov_, Mar 05 2015
%t A121834 fpQ[n_]:=PrimeQ[n]&&PrimeQ[4n^2+1]; Select[4Range[2000]^2+1,fpQ] (* _Harvey P. Dale_, Nov 07 2016 *)
%o A121834 (PARI) isA121834(n)={ if( (n-1) %4, return(0) ; ) ; if( issquare((n-1)/4), if( isprime(4*n^2+1), return(1), return(0) ), return(0) ; ) ; } { for(i=1,1000000, p=prime(i) ; if( isA121834(p), print1(p,",") ; ) ; ) ; } /* _R. J. Mathar_, Sep 01 2006*/
%Y A121834 Cf. A002496, A052291, A121326.
%K A121834 nonn
%O A121834 1,1
%A A121834 _Zak Seidov_, Aug 28 2006
%E A121834 More terms from _R. J. Mathar_, Sep 01 2006