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 A275990 #19 Sep 03 2016 23:53:53
%S A275990 0,0,2,6,18,24,36,42,56,78,82,114,132,138,152,186,212,220,250,278,286,
%T A275990 318,338,368,406,440,454,470,484,500,574,602,632,648,708,712,754,790,
%U A275990 816,848,882,888,960,970,996,1014,1080,1176,1202,1210,1226,1254,1270,1332,1362,1404
%N A275990 a(n) = prime(prime(n)-1) - prime(n).
%F A275990 a(n) = A000040(A006093(n)) - A000040(n) = A055003(n) - A000040(n).
%e A275990 For n=3, prime(prime(3)-1) = 7, and prime(3) = 5, therefore a(3) = 7 - 5 = 2.
%t A275990 Table[Prime[Prime[n]-1] - Prime[n], {n, 1, 100}]
%o A275990 (PARI) a(n) = prime(prime(n)-1) - prime(n); \\ _Michel Marcus_, Aug 18 2016
%Y A275990 Cf. A000040, A006093, A055003, A275989.
%K A275990 nonn
%O A275990 1,3
%A A275990 _Terry D. Grant_, Aug 15 2016