%I #28 Jul 02 2020 13:07:46
%S 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,
%T 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,
%U 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
%N Number of 9's in the decimal expansion of 2^n.
%H Harry J. Smith, <a href="/A065744/b065744.txt">Table of n, a(n) for n = 0..1000</a>
%e 2^12 = 4096 so a(12)=1.
%t Table[ Count[ IntegerDigits[2^n], 9], {n, 0, 100} ]
%o (PARI)
%o Count(x,d)={ #select(t->t==d, digits(x)) }
%o a(n) = Count(2^n, 9) \\ _Harry J. Smith_, Oct 27 2009
%o (Python)
%o def A065744(n):
%o return str(2**n).count('9') # _Chai Wah Wu_, Feb 14 2020
%Y 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.
%K nonn,base
%O 0,33
%A _Benoit Cloitre_, Dec 04 2001
%E More terms from _Robert G. Wilson v_, Dec 07 2001
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