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

1,1

Links

Table of n, a(n) for n=1..55.

Example

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

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 *)

Crossrefs

Cf. A007089, A074940.

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

Sequence in context: A349103 A060914 A242917 * A044059 A287369 A342743

Adjacent sequences: A370918 A370919 A370920 * A370922 A370923 A370924

Keyword

nonn,base

Author

Clark Kimberling, Mar 16 2024

Status

approved