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%I #12 Apr 29 2019 21:07:04
%S 0,1,2,3,4,9,8,7,6,5,10,15,20,21,16,11,12,13,14,19,18,17,22,23,24,49,
%T 48,47,42,43,44,39,38,37,36,41,46,45,40,35,30,31,32,33,34,29,28,27,26,
%U 25,50,75,100,101,76,51,52,53,54,79,78,77,102
%N Base-5 based twisted permutation of the nonnegative integers - variant "Ln".
%C Base-5 variant of Knuth's A220952. The definition of the sequence by an adjacency diagram is the same as in A220952, except that the diagram for the sequence here is:
%C .
%C (0,4)--(1,4) (2,4)--(3,4) (4,4)
%C | | | | |
%C | | | | |
%C (0,3) (1,3) (2,3) (3,3) (4,3)
%C | | | | |
%C | | | | |
%C (0,2) (1,2) (2,2) (3,2)--(4,2)
%C | | |
%C | | |
%C (0,1) (1,1) (2,1)--(3,1)--(4,1)
%C | | |
%C | | |
%C (0,0) (1,0)--(2,0)--(3,0)--(4,0)
%C .
%C Conjecture: As in A220952, it can be proved (a) that every positive integer is adjacent to exactly two nonnegative integers, and (b) that with this definition of adjacency, the nonnegative integers form a path starting with 0.
%C The adjacency definition implies that the terms, when written with 3 base-5 digits, define the coordinates of a self-avoiding, space-filling path in a 5 X 5 X 5 cube. All 3 orthogonal projections to the plane are congruent to the diagram above. This property is maintained in the 4th, 5th ... dimension.
%C The variants of such adjacency diagrams may be distinguished by letter codes, in this case "Ln" with "L" for the path (0,0)...(2,1), and "n" for the path in the upper right corner which has the same shape as the inner structure (1,1)...(3,3) of Knuths's A220952.
%H Georg Fischer, <a href="https://github.com/gfis/fasces">Repository of programs for related sequences</a>, (<a href="https://github.com/gfis/fasces/blob/master/data/gen_paths.pl">gen_paths.pl</a>)
%e In base-5, the terms for the path in two dimensions are 0, 1, 2, 3, 4, 14, 13, 12, 11, 10, 20, 30, 40, 41, 31, 21, 22, 23, 24, 34, 33, 32, 42, 43, 44.
%Y Cf. A220952 (main entry, "Hn"), A307403 ("Hs"), A307405 ("Ls"), A307406 (number of variants per odd base).
%K nonn,base,easy
%O 0,3
%A _Georg Fischer_, Apr 07 2019