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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 (list; graph; refs; listen; history; text; internal format)
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.

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: A302028 A023779 A247812 * A209860 A287513 A194403

Adjacent sequences:  A050721 A050722 A050723 * A050725 A050726 A050727

KEYWORD

nonn,base,more

AUTHOR

Patrick De Geest, Sep 15 1999

STATUS

approved

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Last modified July 15 14:12 EDT 2020. Contains 335772 sequences. (Running on oeis4.)