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 A236603 #20 Mar 07 2022 07:53:58
%S A236603 0,1,0,1,3,2,0,2,3,1,5,4,0,1,3,2,6,7,5,4,0,2,3,7,6,4,5,1,9,8,0,1,3,7,
%T A236603 5,4,6,2,10,11,9,8,0,1,3,2,6,7,5,4,12,13,9,11,10,8,0,1,3,2,6,4,5,7,15,
%U A236603 11,9,13,12,14,10,8,0,2,3,7,5,4,6,14,10,8,12,13,15,11,9,1,17,16
%N A236603 Lowest canonical Gray cycles of length 2n.
%C A236603 See A236602 for definitions regarding canonical Gray sequences (CGC). The CGC's of a given length can be sorted 'lexically'; for example, the CGC {0 1 5 4 6 7 3 2} precedes {0 1 5 7 3 2 6 4}. This sequence is then the flattened triangular table of the terms of the lowest CGC for each even length L, where L = 2*<row index>.
%C A236603 Note: zero unequivocally marks the start of each CGC.
%H A236603 Martin Ehrenstein, <a href="/A236603/b236603.txt">Table of n, a(n) for n = 1..1056</a> (first 306 terms from Stanislav Sykora)
%H A236603 Martin Ehrenstein, <a href="/A236603/a236603_1.txt">Triangle for A236603</a> (first 17 rows from Stanislav Sykora)
%H A236603 Stanislav Sykora, <a href="http://dx.doi.org/10.3247/SL5Math14.001">On Canonical Gray Cycles</a>, Stan's Library, Vol.V, January 2014, DOI: 10.3247/SL5Math14.001
%e A236603 L CGC
%e A236603 2 0, 1
%e A236603 4 0, 1, 3, 2
%e A236603 6 0, 2, 3, 1, 5, 4
%e A236603 8 0, 1, 3, 2, 6, 7, 5, 4
%e A236603 10 0, 2, 3, 7, 6, 4, 5, 1, 9, 8
%Y A236603 Cf. A236602 (CGC counts).
%K A236603 nonn,tabf,hard
%O A236603 1,5
%A A236603 _Stanislav Sykora_, Feb 01 2014