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 A181494 #8 Aug 06 2025 22:36:14 %S A181494 5,7,11,13,191,193,786431,786433 %N A181494 Twin primes (A001097) of the form 3*2^k +- 1. %F A181494 A181494 = A181491 union A181492. %F A181494 A181494(n) = A181493(ceiling(n/2)) + (-1)^n = A007283(A181490(ceiling(n/2))) + (-1)^n. %o A181494 (PARI) for( k=1,999, ispseudoprime(3<<k-1)||next; ispseudoprime(3<<k+1)||next; print1(3<<k-1,", ",3<<k+1,", ")) %Y A181494 Cf. A001097, A001359, A006512, A014574. %K A181494 more,nonn %O A181494 1,1 %A A181494 _M. F. Hasler_, Oct 30 2010