A065717 - OEIS

A065717

Number of 6's in decimal expansion of 2^n.

0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 1, 2, 0, 1, 0, 1, 0, 0, 1, 2, 0, 2, 0, 2, 1, 0, 1, 2, 0, 1, 1, 3, 0, 1, 0, 2, 0, 1, 1, 2, 0, 3, 0, 3, 1, 2, 1, 2, 0, 0, 3, 1, 0, 1, 2, 4, 1, 3, 1, 3, 1, 4, 2, 1, 1, 1, 3, 6, 1, 1, 3, 2, 2, 3, 2, 4, 1, 2, 4, 3, 6, 3, 2, 2, 4, 0, 1, 4, 0, 3, 4, 3, 3, 2, 3, 5

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

OFFSET

0,17

LINKS

Harry J. Smith, Table of n, a(n) for n = 0..1000

EXAMPLE

2^8 = 256 so a(8)=1.

MATHEMATICA

Table[ Count[ IntegerDigits[2^n], 6], {n, 0, 100} ]

DigitCount[#, 10, 6]&/@(2^Range[0, 100]) (* Harvey P. Dale, Feb 15 2020 *)

PROG

(PARI) a(n) = #select(x->(x==6), digits(2^n)); \\ Andrew Howroyd, Apr 25 2020