A050724 Numbers k such that the decimal expansion of 3^k contains no pair of consecutive equal digits (probably finite).

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 13, 14, 15, 16, 17, 18, 21, 22, 24, 26, 42, 66, 67, 133

Offset

1,3

Comments

No additional terms up to 50000. - Harvey P. Dale, Nov 15 2011

No additional terms up to 100000. - Michel Marcus, Oct 16 2019

Links

Table of n, a(n) for n=1..25.

Example

3^133 = 2865014852390475710679572105323242035759805416923029389510561523.

Maple

q:= n-> (s-> andmap(i-> s[i]<>s[i+1], [$1..length(s)-1]))(""||(3^n)):
select(q, [$0..200])[];  # Alois P. Heinz, Mar 07 2024

Mathematica

Select[Range[0, 500], !MemberQ[Differences[IntegerDigits[3^#]], 0]&] (* Harvey P. Dale, Nov 15 2011 *)

Prog

(PARI) isok(n) = {my(d = digits(3^n), c = d[1]); for (i=2, #d, if (d[i] == c, return (0)); c = d[i]; ); return (1); } \\ Michel Marcus, Oct 16 2019

Crossrefs

Cf. A000244, A030700, A046261, A046269.

Sequence in context: A023779 A367611 A247812 * A336813 A209860 A287513

Adjacent sequences: A050721 A050722 A050723 * A050725 A050726 A050727

Keyword

nonn,base,more

Author

Patrick De Geest, Sep 15 1999

Status

approved