A065744 Number of 9's in the decimal expansion of 2^n.

0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 3, 3, 2, 1, 1, 1, 2, 1, 2, 2, 1, 2, 1, 0, 0, 0, 1, 3, 3, 2, 3, 5, 3, 3, 3, 0, 0, 0, 2, 3, 1, 1, 1, 2, 2, 3, 3, 2, 1, 0, 2, 5, 2, 3, 2, 0, 2, 2, 3, 3, 1, 4, 3, 2, 1, 2, 2, 4, 4, 2, 6, 8, 3, 3, 3, 1, 1, 0, 2

Offset

0,33

Links

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

Example

2^12 = 4096 so a(12)=1.

Mathematica

Table[ Count[ IntegerDigits[2^n], 9], {n, 0, 100} ]

Prog

(PARI)
Count(x, d)={ #select(t->t==d, digits(x)) }
a(n) = Count(2^n, 9) \\ Harry J. Smith, Oct 27 2009
(Python)
def A065744(n):
    return str(2**n).count('9')  # Chai Wah Wu, Feb 14 2020

Crossrefs

Cf. 0's A027870, 1's A065712, 2's A065710, 3's A065714, 4's A065715, 5's A065716, 6's A065717, 7's A065718, 8's A065719.

Sequence in context: A056223 A261143 A100013 * A016455 A278702 A060574

Adjacent sequences: A065741 A065742 A065743 * A065745 A065746 A065747

Keyword

nonn,base

Author

Benoit Cloitre, Dec 04 2001

Extensions

More terms from Robert G. Wilson v, Dec 07 2001

Status

approved