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 A181492 #24 Aug 06 2025 22:36:23
%S A181492 7,13,193,786433
%N A181492 Primes of the form p=3*2^k+1 such that p-2 is also a prime.
%C A181492 Sequence A181490 lists the exponents k, sequences A181491 and A181493 the corresponding lesser twin prime and their average.
%C A181492 a(5) > 3 * 2^3000 + 1. - _Max Z. Scialabba_, Dec 24 2023
%F A181492 A181492 = A181491 + 2 = A181493 + 1 = 3*2^A181490 + 1 = intersection of A004119 or A103204 or A181495 with A006512 or A001097.
%t A181492 Select[3 2^Range[100]+1,And@@PrimeQ[{#,#-2}]&] (* _Harvey P. Dale_, Jun 19 2013 *)
%o A181492 (PARI) for( k=1,999, ispseudoprime(3<<k-1)||next; ispseudoprime(3<<k+1)||next; print1(3<<k+1,", "))
%Y A181492 Cf. A001097, A001359, A006512, A014574.
%K A181492 nonn
%O A181492 1,1
%A A181492 _M. F. Hasler_, Oct 30 2010