A263307 Numbers without consecutive repeated digits in base 2 and in base 3.

1, 2, 5, 10, 21, 1365, 2730

Offset

1,2

Comments

Intersection of A000975 and A031941. - Michel Marcus, Oct 14 2015

It seems likely that there are no further terms.

Links

Table of n, a(n) for n=1..7.

Example

10 is 1010 in base 2 and 101 in base 3; no two of the same digit are next to one another and so 10 is a term.
Similarly 21 is 10101 in base 2 and 210 in base 3 so it is also a term.

Prog

(PARI) isokd(d) = {dd = vector(#d-1, k, abs(d[k+1]-d[k])); if (#dd, vecmin(dd), 1); }
isok(n) = isokd(binary(n)) && isokd(digits(n, 3)); \\ Michel Marcus, Oct 14 2015

Crossrefs

Cf. A000975 (base 2), A031941 (base 3).

Sequence in context: A361779 A360748 A151497 * A278441 A323939 A110744

Adjacent sequences: A263304 A263305 A263306 * A263308 A263309 A263310

Keyword

nonn,base

Author

Robin Powell, Oct 13 2015

Status

approved