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 A044972 #23 Jul 26 2023 03:20:56 %S A044972 10,12,32,34,38,42,46,48,58,64,66,98,104,106,116,128,132,140,142,146, %T A044972 150,154,156,176,178,184,194,196,200,204,208,210,220,226,228,296,314, %U A044972 320,322,350,386,398,402,422,428,430,440,452 %N A044972 Numbers whose base-3 representation contains exactly one 0 and two 1's. %H A044972 David A. Corneth, <a href="/A044972/b044972.txt">Table of n, a(n) for n = 1..10000</a> %t A044972 Select[Range[500],DigitCount[#,3,0]==1&&DigitCount[#,3,1]==2&] (* _Harvey P. Dale_, Aug 19 2019 *) %o A044972 (PARI) is(n)=my(d=digits(n,3),fr=vector(3));for(i=1,#d,fr[d[i]+1]++);fr[1]==1&&fr[2]==2 \\ _David A. Corneth_, Aug 19 2019 %Y A044972 Cf. A007089, A024023. %K A044972 nonn,easy,base %O A044972 1,1 %A A044972 _Clark Kimberling_