A223077 Positive integers, written in base 3, with the property that if the base-3 representation is reversed the result is twice the original number.

1012, 10212, 102212, 1022212, 10121012, 10222212, 101201012, 102222212, 1012001012, 1021210212, 1022222212, 10120001012, 10212010212, 10222222212, 101200001012, 101210121012, 102120010212, 102212102212, 102222222212, 1012000001012, 1012102121012, 1021200010212, 1022120102212, 1022222222212

Offset: 1

Author

N. J. A. Sloane, Mar 14 2013

Keywords

• nonn
• base

Comments

For the decimal representations of these same numbers see A173951.

Theorem: The number of terms of length n is equal to A103609(n-2).

Links

• N. J. A. Sloane, Table of n, a(n) for n = 1..108

Crossrefs

Cf. A173951, A214927.

Programs

Mathematica

b3rQ[n_]:=FromDigits[Reverse[IntegerDigits[n]],3]/FromDigits[ IntegerDigits[ n],3] ==2; Select[FromDigits/@Tuples[{0,1,2},13],b3rQ]//Quiet (* Harvey P. Dale, Jun 10 2018 *)