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 A187872 #10 Nov 05 2020 05:36:37 %S A187872 3,5,7,13,19,41,71,137,263,523,1033,2063,4111,8219,16417,32779,65539, %T A187872 131111,262151,524341,1048589,2097211,4194329,8388619,16777289, %U A187872 33554473,67108913,134217773,268435463,536870951,1073741831,2147483693 %N A187872 Second smallest prime after 2^n. %H A187872 Robert Israel, <a href="/A187872/b187872.txt">Table of n, a(n) for n = 0..3318</a> %e A187872 2^2=4, second smallest prime=7; %e A187872 2^3=8, second smallest prime=13; .. %p A187872 seq(nextprime(nextprime(2^n)),n=0..100); # _Robert Israel_, Nov 04 2020 %t A187872 NextPrime[2^Range[0,100], 2] %o A187872 (PARI) a(n) = nextprime(nextprime(2^n+1)+1); \\ _Michel Marcus_, Nov 05 2020 %Y A187872 Cf. A007491, A014210. %K A187872 nonn %O A187872 0,1 %A A187872 _Vladimir Joseph Stephan Orlovsky_, Mar 14 2011