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 A059137 #18 Sep 13 2022 09:35:55
%S A059137 18,54,18,90,18,54,18,126,18,54,18,90,18,54,18,162,18,54,18,90,18,54,
%T A059137 18,126,18,54,18,90,18,54,18,198,18,54,18,90,18,54,18,126,18,54,18,90,
%U A059137 18,54,18,162,18,54,18,90,18,54,18,126,18,54,18,90,18,54,18,234,18,54
%N A059137 A hierarchical sequence (W3{2,2}cc - see A059126).
%H A059137 Jonas Wallgren, <a href="/A059126/a059126.txt">Hierarchical sequences</a>
%F A059137 a(n) = 18*A037227(n). - _Mitch Harris_, Jun 29 2005
%F A059137 a(n) = A059136(3*n) + A059136(3*n+1) + A059136(3*n+2). - _Sean A. Irvine_, Sep 13 2022
%Y A059137 Cf. A037227, A059126, A059136.
%K A059137 easy,nonn
%O A059137 0,1
%A A059137 _Jonas Wallgren_, Jan 19 2001