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 A249728 #9 Nov 24 2018 15:31:09
%S A249728 1,2,3,3,4,4,5,5,5,6,6,6,7,7,7,7,8,8,8,8,9,9,9,9,10,10,10,10,11,11,11,
%T A249728 11,11,12,12,12,12,12,13,13,13,13,13,13,14,14,14,14,14,14,15,15,15,15,
%U A249728 15,15,16,16,16,16,16,16,17,17,17,17,17,17,17,18,18,18,18,18,18,18,19,19,19,19,19,19,19,19,20,20,20,20,20,20,20,20
%N A249728 After a(1) = 1 each n appears A000720(n) times.
%H A249728 Antti Karttunen, <a href="/A249728/b249728.txt">Table of n, a(n) for n = 1..10016</a>
%t A249728 Join[{1},Table[Table[n,PrimePi[n]],{n,20}]//Flatten] (* _Harvey P. Dale_, Nov 24 2018 *)
%o A249728 (Scheme, with _Antti Karttunen_'s IntSeq-library)
%o A249728 (define A249727 (COMPOSE (LEAST-GTE-I 0 1 A046992) -1+)) ;; One-based.
%Y A249728 Cf. A000720, A046992, A249727, A249809.
%K A249728 nonn
%O A249728 1,2
%A A249728 _Antti Karttunen_, Nov 06 2014