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 A217373 #28 Feb 15 2017 02:17:00 %S A217373 9,18,27,36,45,54,63,72,90,99,108,117,126,135,144,153,171,180,189,198, %T A217373 207,216,225,234,252,261,270,279,288,297,306,315,333,342,351,360,369, %U A217373 378,387,396,414,423,432,441,450,459,468,477,495,504,513,522,531,540 %N A217373 Numbers n the representation of which in base 3 ends in 2*k or 2*k+1 zeros, where k is odd. %C A217373 Or numbers having infinitary divisor 9, or the same having factor 9 in their Fermi-Dirac factorization as product of distinct terms of A050376. %H A217373 Peter J. C. Moses, <a href="/A217373/b217373.txt">Table of n, a(n) for n = 1..10000</a> %H A217373 <a href="/index/Ar#3-automatic">Index entries for 3-automatic sequences</a>. %F A217373 a(n)/(10*n) tends to 1, as n goes to infinity. %t A217373 Select[Map[# Boole[IntegerQ[(1/4 (1+#))]||IntegerQ[(1/4 (2+#))]&[Length[Last[Split[IntegerDigits[#,3]]]]]]&,Range[3,5000,3]],#>0&] (* _Peter J. C. Moses_, Mar 20 2013 *) %Y A217373 Cf. A145204, A217319, A036554, A050376. %K A217373 nonn,easy %O A217373 1,1 %A A217373 _Vladimir Shevelev_, Mar 18 2013