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 A177691 #8 Feb 13 2019 16:34:07 %S A177691 1,3,3,5,5,7,7,9,9,9,9,9,9,11,11,11,11,11,11,13,13,15,15,15,15,15,15, %T A177691 17,17,19,19,19,19,21,21,21,21,21,21,23,23,23,23,23,23,25,25,25,25,27, %U A177691 27,27,27,29,29,29,29,31,31,31,31,33,33,35,35,37,37,37,37,37,37,39,39,39 %N A177691 The odd values of PrimePi(.), with repetition. %H A177691 Robert Israel, <a href="/A177691/b177691.txt">Table of n, a(n) for n = 1..10000</a> %F A177691 Obtained by removing all even numbers from A000720. Block lengths (frequencies of repetitions) are in A078584. %p A177691 seq((2*n-1)$(ithprime(2*n)-ithprime(2*n-1)),n=1..30); # _Robert Israel_, Feb 13 2019 %t A177691 Select[PrimePi[Range[300]],OddQ] (* _Harvey P. Dale_, Dec 24 2014 *) %Y A177691 Cf. A000720, A005408. %K A177691 nonn,easy %O A177691 1,2 %A A177691 _Giovanni Teofilatto_, May 11 2010 %E A177691 Erroneous formula removed by _R. J. Mathar_, May 14 2010