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

Author

Patrick De Geest, Sep 15 1999

Keywords

• nonn
• base
• more

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

Examples

			4^63 = 85070591730234615865843651857942052864.
		

Crossrefs

Cf. A000302, A030701, A046262, A046270.

Programs

Mathematica

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

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