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 A023694 #11 Mar 15 2020 10:30:47 %S A023694 13,31,37,39,41,43,49,67,85,91,93,95,97,103,109,111,113,115,117,119, %T A023694 123,125,127,129,131,133,139,145,147,149,151,157,175,193,199,201,203, %U A023694 205,211,229,247,253,255,257,259,265,271,273,275,277,279,281,285,287,289 %N A023694 Numbers with exactly 3 1's in ternary expansion. %H A023694 Alois P. Heinz, <a href="/A023694/b023694.txt">Table of n, a(n) for n = 1..10000</a> %p A023694 q:= n-> numboccur(1, convert(n, base, 3))=3: %p A023694 select(q, [$1..300])[]; # _Alois P. Heinz_, Mar 15 2020 %t A023694 Select[ Range[ 270 ], (Count[ IntegerDigits[ #, 3 ], 1 ]==3)& ] %K A023694 nonn,base,easy %O A023694 1,1 %A A023694 _Olivier Gérard_