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 A057202 #16 Aug 08 2016 12:51:13
%S A057202 1,2,3,4,5,6,7,9,11,13,14,21,23,41,46,89,110,389,413,489,869,1589,
%T A057202 1713,2831,10843,11257,16949,24513,39621,43349,62941,96094,139237,
%U A057202 145289,264683,396790
%N A057202 Numbers n such that 2^n - 21 is prime.
%C A057202 The first four terms correspond to negative primes. Dropping them gives A096820. - _Joerg Arndt_, Oct 05 2012
%t A057202 Do[ If[ PrimeQ[ 2^n - 21 ], Print[ n ] ], {n, 1, 3000} ]
%o A057202 (PARI) is(n)=isprime(2^n - 21) \\ _Charles R Greathouse IV_, Aug 08 2016
%Y A057202 Cf. A096820.
%K A057202 nonn
%O A057202 1,2
%A A057202 _Robert G. Wilson v_, Sep 16 2000
%E A057202 a(25)-a(34) from A096820, by _Bruno Berselli_, Oct 05 2012
%E A057202 a(35)-a(36) from A096820, by _Robert Price_, Aug 08 2016