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 A276660 #8 Sep 11 2016 17:07:09 %S A276660 2,5,11,13,19,23,37,43,47,61,67,73,79,103,151,157,163,191,193,211,223, %T A276660 271,277,283,313,331,367,383,397,421,457,463,487,523,541,547,607,613, %U A276660 631,661,673,691,733,751,757,787,823,877,907,991,997,1051,1087,1093,1123 %N A276660 Primes of the form p*2^k - 1 where p is an odd prime and k >= 0. %F A276660 a(n) >> n (log n)^2. - _Charles R Greathouse IV_, Sep 11 2016 %e A276660 2 is in this sequence because 3*2^0 - 1 = 2 is prime. %e A276660 5 is in this sequence because 3*2^1 - 1 = 5 is prime. %e A276660 11 is in this sequence because 3*2^2 - 1 = 11 is prime. %o A276660 (PARI) is(n)=isprime((n+1)>>valuation(n+1,2)) && isprime(n) \\ _Charles R Greathouse IV_, Sep 11 2016 %Y A276660 Essentially the same as A192869 and A206581. %Y A276660 Cf. A038550, A058500. %K A276660 nonn %O A276660 1,1 %A A276660 _Juri-Stepan Gerasimov_, Sep 11 2016