A303446 Lexicographically first sequence of distinct terms such that a(n) can be recreated concatenating [the last digit(s) of a(n-1)] to [the first digit(s) of a(n+1)].

1, 11, 12, 21, 13, 31, 14, 41, 15, 51, 16, 61, 17, 71, 18, 81, 19, 91, 110, 101, 111, 112, 22, 23, 32, 24, 42, 25, 52, 26, 62, 27, 72, 28, 82, 29, 92, 210, 102, 211, 113, 33, 34, 43, 35, 53, 36, 63, 37, 73, 38, 83, 39, 93, 310, 103, 311, 114, 44, 45, 54, 46, 64, 47, 74, 48, 84, 49, 94, 410, 104, 411

Offset: 1

Author

Jean-Marc Falcoz and Eric Angelini, Apr 24 2018

Keywords

• nonn
• base

Comments

The sequence is started with a(1) = 1 and always extended with the smallest term not present that doesn't lead to a contradiction.

Examples

			a(2) = 11  is [1] concatenated to [the first 1 of 12];
a(3) = 12  is [the last 1 of 11] concatenated to [the 2 of 21];
a(4) = 21  is [the 2 of 12] concatenated to [the 1 of 13];
a(5) = 13  is [the 1 of 21] concatenated to [the 3 of 31];
a(6) = 31  is [the 3 of 13] concatenated to [the 1 of 14];
a(7) = 14  is [the 1 of 31] concatenated to [the 4 of 41];
etc.
		

Links

• Jean-Marc Falcoz, Table of n, a(n) for n = 1..4003