A065714 Number of 3's in decimal expansion of 2^n.

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

Offset

0,26

Links

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

Example

2^5 = 32 so a(5)=1.

Mathematica

Table[ Count[ IntegerDigits[2^n], 3], {n, 0, 100} ]

Prog

(PARI) a(n) = #select(x->(x==3), digits(2^n)); \\ Michel Marcus, Jun 15 2018
(Python)
def A065714(n):
    return str(2**n).count('3') # Chai Wah Wu, Feb 14 2020

Crossrefs

Cf. 0's A027870, 1's A065712, 2's A065710, 4's A065715, 5's A065716, 6's A065717, 7's A065718, 8's A065719, 9's A065744.

Sequence in context: A101949 A124796 A343858 * A110700 A375032 A338939

Adjacent sequences: A065711 A065712 A065713 * A065715 A065716 A065717

Keyword

nonn,base

Author

Benoit Cloitre, Dec 04 2001

Extensions

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

Status

approved