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 A112231 #6 Aug 12 2019 19:07:20
%S A112231 1,2,2,3,3,4,5,5,6,7,7,8,9,10,11,11,12,13,13,14,15,16,17,17,18,19,19,
%T A112231 20,21,22,23,23,24,25,26,27,28,29,29,30,31,31,32,33,34,35,36,37,37,38,
%U A112231 39,40,41,41,42,43,43,44,45,46,47,47,48,49,50,51,52,53,53,54,55,56,57,58
%N A112231 Repeat each prime in the sequence of natural numbers.
%C A112231 a(n) = A112233(n) - A112232(n);
%C A112231 a(n + A000040(n) - 1) = A000040(n),
%C A112231 a(n + A000040(n)) = A000040(n),
%C A112231 a(n + A000040(n) + 1) = A000040(n) + 1.
%t A112231 Table[If[PrimeQ[n],{n,n},n],{n,70}]//Flatten (* _Harvey P. Dale_, Aug 12 2019 *)
%Y A112231 Cf. A109763.
%K A112231 nonn
%O A112231 1,2
%A A112231 _Reinhard Zumkeller_, Aug 29 2005