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%I #12 Feb 07 2021 17:04:45
%S 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,21,20,11,31,23,22,24,
%T 25,26,27,28,29,32,30,12,41,34,33,35,36,37,38,39,43,40,13,51,45,42,44,
%U 46,47,48,49,54,50,14,61,56,52,53,55,57,58,59,65,60,15,71,67,62,63,64,66,68,69,76,70,16,81,78,72
%N If a(n) has at least one common digit with a(n-1), underline a(n). The non-underlined terms reproduce the sequence itself.
%C This is a kind of fractal sequence as it contains an infinite number of copies of itself. The underlined terms of the sequence are the lexicographically earliest permutation of the natural numbers > 10.
%e If we erase the parenthesized terms, we get the sequence itself: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, (11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 20), 11, (31, 23, 22, 24, 25, 26, 27, 28, 29, 32, 30), 12, (41, 34, 33, 35, 36, 37, 38, 39, 43, 40), 13, (51, 45, 42, 44, 46, 47, 48, 49, 54, 50), 14, (61, 56, 52, 53, 55, 57, 58, 59, 65, 60), 15, (71, 67, 62, 63, 64, 66, 68, 69, 76, 70), 16, (81, 78, 72, ...) etc.
%Y Cf. A274329.
%K base,nonn
%O 1,2
%A _Eric Angelini_, Oct 19 2020
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