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 A275988 #12 Sep 03 2016 23:52:36
%S A275988 3,10,18,30,36,48,56,70,80,84,106,114,126,138,150,170,174,190,202,210,
%T A275988 234,238,264,270,282,296,316,326,340,350,360,372,386,418,422,442,450,
%U A275988 456,476,486,498,520,536,550,564,588,600,604,626,634,650,672,696,702,720,734,750,762,774
%N A275988 a(n) = prime(3n) - prime(n).
%F A275988 a(n) = A031336(n) - A000040(n).
%e A275988 For n=3, prime(3n) = 23, and prime(n) = 5, therefore a(3) = 23 - 5 = 18.
%t A275988 Table[Prime[3n] - Prime[n], {n, 1, 100}]
%o A275988 (PARI) a(n) = prime(3*n) - prime(n); \\ _Michel Marcus_, Aug 18 2016
%Y A275988 Cf. A000040, A031336, A072473.
%K A275988 nonn
%O A275988 1,1
%A A275988 _Terry D. Grant_, Aug 15 2016