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

Author

Patrick De Geest, Sep 15 1999

Keywords

• nonn
• base
• more

Comments

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

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

Examples

			3^133 = 2865014852390475710679572105323242035759805416923029389510561523.
		

Crossrefs

Cf. A000244, A030700, A046261, A046269.

Programs

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 *)

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