

A050724


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


3



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
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OFFSET

1,3


COMMENTS



LINKS



EXAMPLE

3^133 = 2865014852390475710679572105323242035759805416923029389510561523.


MAPLE

q:= n> (s> andmap(i> s[i]<>s[i+1], [$1..length(s)1]))(""(3^n)):


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



KEYWORD

nonn,base,more


AUTHOR



STATUS

approved



