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%I #26 Apr 25 2020 13:32:42
%S 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,
%T 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,
%U 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
%N Number of 3's in decimal expansion of 2^n.
%H Harry J. Smith, <a href="/A065714/b065714.txt">Table of n, a(n) for n = 0..1000</a>
%e 2^5 = 32 so a(5)=1.
%t Table[ Count[ IntegerDigits[2^n], 3], {n, 0, 100} ]
%o (PARI) a(n) = #select(x->(x==3), digits(2^n)); \\ _Michel Marcus_, Jun 15 2018
%o (Python)
%o def A065714(n):
%o return str(2**n).count('3') # _Chai Wah Wu_, Feb 14 2020
%Y 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.
%K nonn,base
%O 0,26
%A _Benoit Cloitre_, Dec 04 2001
%E More terms from _Robert G. Wilson v_, Dec 07 2001
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