A370921 Positive integers in whose ternary representation, 2 occurs at least once, and every 2 is followed by 1.

7, 16, 21, 22, 34, 43, 48, 49, 63, 64, 66, 67, 70, 88, 97, 102, 103, 115, 124, 129, 130, 144, 145, 147, 148, 151, 189, 190, 192, 193, 196, 198, 199, 201, 202, 205, 210, 211, 250, 259, 264, 265, 277, 286, 291, 292, 306, 307, 309, 310, 313, 331, 340, 345, 346

Offset: 1

Author

Clark Kimberling, Mar 16 2024

Keywords

• nonn
• base

Examples

			The ternary representations of 7, 16, and 21 are 21, 121, and 210.
		

Crossrefs

Cf. A007089, A074940.

Cf. A370916, A370917, A370918, A370919, A370920, A370922, A370923.

Programs

Mathematica

Map[#[[1]] &, Select[Map[{#, #[[1]] > 0 && #[[1]] == #[[2]] &[{Length[
StringCases[#, "2"]], Length[StringCases[#, "21"]]}] &[
IntegerString[#, 3]]} &, Range[500]], #[[2]] &]]
  (* Peter J. C. Moses, Mar 05 2024 *)