cp's OEIS Frontend

A065716 Number of 5's in decimal expansion of 2^n.

%I A065716 #28 Nov 13 2021 13:26:06
%S A065716 0,0,0,0,0,0,0,0,1,1,0,0,0,0,0,0,2,0,0,1,1,1,0,0,0,2,0,0,2,1,0,0,0,2,
%T A065716 0,1,0,1,0,3,1,4,1,0,1,1,0,2,1,2,1,2,2,1,1,0,2,4,1,2,2,2,0,2,2,0,0,3,
%U A065716 5,5,1,0,1,1,3,2,4,3,3,2,1,3,3,2,1,3,4,4,3,1,1,3,4,1,3,2,4,5,5,2,2
%N A065716 Number of 5's in decimal expansion of 2^n.
%H A065716 Harry J. Smith, <a href="/A065716/b065716.txt">Table of n, a(n) for n = 0..1000</a>
%e A065716 2^8 = 256 so a(8)=1.
%t A065716 Table[ Count[ IntegerDigits[2^n], 5], {n, 0, 100} ]
%t A065716 DigitCount[#,10,5]&/@(2^Range[0,100]) (* _Harvey P. Dale_, Nov 13 2021 *)
%o A065716 (PARI) a(n) = #select(x->(x==5), digits(2^n)); \\ _Michel Marcus_, Jun 15 2018
%o A065716 (Python)
%o A065716 def A065716(n):
%o A065716     return str(2**n).count('5') # _Chai Wah Wu_, Feb 14 2020
%Y A065716 Cf. 0's A027870, 1's A065712, 2's A065710, 3's A065714, 4's A065715, 6's A065717, 7's A065718, 8's A065719, 9's A065744.
%K A065716 nonn,base
%O A065716 0,17
%A A065716 _Benoit Cloitre_, Dec 04 2001
%E A065716 More terms from _Robert G. Wilson v_, Dec 07 2001