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 A196446 #11 Sep 06 2017 11:29:23 %S A196446 2,3,19,29,43,61,79,109,151,167,2311 %N A196446 Numbers n such that both n and (n-1)^2*2^n-1 are primes. %C A196446 Primes p such that (p-1)^2*2^p-1 is also prime. %e A196446 a(1)=2 because 2 is a prime and (2-1)^2*2^2-1=3 is a prime, %e A196446 a(2)=3 because 3 is a prime and (3-1)^2*2^3-1=31 is a prime, %e A196446 a(3)=19 because 19 is a prime and (19-1)^2*2^19-1=169869313 is a prime, %e A196446 a(4)=29 because 29 is a prime and (29-1)^2*2^29-1=420906795007 is a prime. %t A196446 Select[Prime[Range[40]],PrimeQ[(#-1)^2 2^#-1]&] (* The program generates the first 10 terms *) (* _Harvey P. Dale_, Sep 06 2017 *) %K A196446 nonn %O A196446 1,1 %A A196446 _Juri-Stepan Gerasimov_, Oct 02 2011