A050725 Decimal expansion of 4^n contains no pair of consecutive equal digits (probably finite).

0, 1, 2, 3, 4, 5, 6, 7, 10, 11, 14, 15, 16, 17, 18, 24, 27, 28, 33, 34, 40, 52, 63

Offset

1,3

Comments

No additional terms up to 1200. - Harvey P. Dale, Mar 30 2011

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

Half of even terms of A050723. - Joerg Arndt, Oct 16 2019

Links

Table of n, a(n) for n=1..23.

Example

4^63 = 85070591730234615865843651857942052864.

Mathematica

Select[Range[0, 70], FreeQ[Differences[IntegerDigits[4^#]], 0]&] (* Harvey P. Dale, Jul 25 2013 *)

Prog

(PARI) isok(n) = {my(d = digits(4^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. A000302, A030701, A046262, A046270.

Sequence in context: A116000 A251595 A373789 * A080571 A165805 A319975

Adjacent sequences: A050722 A050723 A050724 * A050726 A050727 A050728

Keyword

nonn,base,more

Author

Patrick De Geest, Sep 15 1999

Status

approved