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 A124521 #18 Dec 17 2019 07:39:57
%S A124521 12,15,27,72,93,117,132,162,168,195,198,210,258,267,300,327,330,345,
%T A124521 435,468,642,765,813,855,903,912,960,978,993,1128,1143,1182,1290,1350,
%U A124521 1353,1365,1392,1398,1440,1632,1680,1713,1737,1797,1848,1860,1947,1953,1962
%N A124521 Numbers k such that 16*k - 1 and 16*k + 1 are twin primes.
%H A124521 Amiram Eldar, <a href="/A124521/b124521.txt">Table of n, a(n) for n = 1..10000</a>
%e A124521 12 is in the sequence since 16*12 - 1 = 191 and 16*12 + 1 = 193 are twin primes.
%p A124521 A124521:=n->`if`(isprime(16*n-1) and isprime(16*n+1), n, NULL): seq(A124521(n), n=1..2000); # _Wesley Ivan Hurt_, Oct 10 2014
%t A124521 Select[Range[2000], And @@ PrimeQ[{-1, 1} + 16# ] &] (* _Ray Chandler_, Nov 16 2006 *)
%Y A124521 Cf. A040040, A045753, A002822, A124065, A124518, A124519, A124520, A124522, A063983.
%K A124521 nonn
%O A124521 1,1
%A A124521 _Artur Jasinski_, Nov 04 2006
%E A124521 Extended by _Ray Chandler_, Nov 16 2006