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 A176569 #15 Feb 10 2019 00:42:08
%S A176569 1,6,6,12,12,18,18,24,28,32,36,42,42,48,52,60,60,68,70,74,78,84,88,98,
%T A176569 100,104,106,110,112,128,130,138,138,150,150,158,162,168,172,180,180,
%U A176569 192,192,198,198,212,222,228,228,234,238,242,250,258,262,270,270,278
%N A176569 a(n) = (-1)^n + (n-th prime of the form 3k-+1).
%H A176569 Michael De Vlieger, <a href="/A176569/b176569.txt">Table of n, a(n) for n = 1..10001</a>
%F A176569 a(n) = (-1)^n + A045344(n). - _Michel Marcus_, Feb 07 2019
%p A176569 A045344 := proc(n) if n = 1 then 2; else ithprime(n+1) ; end if; end proc:
%p A176569 A176569 := proc(n) (-1)^n+A045344(n) ; end proc:
%p A176569 seq(A176569(n),n=1..120) ; # _R. J. Mathar_, Apr 27 2010
%t A176569 Total /@ Nest[Append[#1, Block[{p = NextPrime@ #1[[-1, -1]]}, While[Mod[p, 3] == 0, p = NextPrime@ p]; {(-1)^#2, p}]] & @@ {#, Length@ # + 1} &, {{-1, 2}}, 57] (* _Michael De Vlieger_, Feb 09 2019 *)
%o A176569 (PARI) a045344(n) = if(n<2, 2, prime(n+1));
%o A176569 a(n) = (-1)^n + a045344(n); \\ _Michel Marcus_, Feb 07 2019
%Y A176569 Cf. A045344.
%K A176569 nonn
%O A176569 1,2
%A A176569 _Juri-Stepan Gerasimov_, Apr 20 2010
%E A176569 Corrected (double-5 replaced by double-6, 146 removed) by _R. J. Mathar_, Apr 27 2010