A369303 a(1) = 1, a(2) = 2; for n > 2, a(n) is the smallest unused number whose string value contains the comma transform (cf. A367360) of the previous two terms.

1, 2, 12, 21, 22, 112, 121, 210, 120, 10, 11, 13, 110, 31, 3, 113, 131, 231, 122, 111, 211, 123, 114, 310, 43, 4, 34, 143, 41, 134, 115, 141, 51, 15, 116, 151, 61, 16, 117, 161, 71, 17, 118, 171, 81, 18, 119, 181, 91, 19, 311, 93, 190, 312, 23, 220, 32, 30, 223, 20, 132, 14, 212, 42, 24, 221

Offset: 1

Author

Scott R. Shannon, Jan 19 2024

Keywords

• nonn
• base
• look

Comments

The sequence is conjectured to be a permutation of the positive integers. The fixed points begin 1, 2, 10, 11, 2863, 3164, 3545, 3947, 6835, 6947, 7052, ... although it is likely there are infinitely more.

Examples

			a(3) = 12 as the comma transform of 1 and 2 is 12.
a(6) = 112 as the comma transform of 21 and 22 is 12, but 12 has already appeared so the next lowest unused number to contain '12' is 112.
		

Links

• Scott R. Shannon, Table of n, a(n) for n = 1..10000
• Scott R. Shannon, Image of the first one million terms. The green line is a(n) = n.

Crossrefs

Cf. A367360, A121805, A367362.