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%I #30 Nov 21 2021 07:34:55
%S 1,1,1,1,2,2,2,3,4,5,5,6,7,8,9,10,11,12,13,15,15,16,18,19,20,20,21,23,
%T 24,25,26,27,29,30,32,33,34,36,37,39,39,41,43,44,46,47,48,50,52,53,53,
%U 55,56,58,60,61,62,64,66,68,68,70,72,74,76,76,78,80,82,84,85,86,88,90,92,92,94
%N Number of digits in n! excluding final zeros.
%C From _Bernard Schott_, Nov 19 2021: (Start)
%C a(n) < n iff 2 <= n <= 38 or n = 40;
%C a(n) = n iff n = 1, 39, 41;
%C a(n) > n iff n = 0 or n >= 42. (End)
%H T. D. Noe, <a href="/A008906/b008906.txt">Table of n, a(n) for n = 0..1000</a>
%H <a href="/index/Fi#final">Index entries for sequences related to final digits of numbers</a>
%F a(n) = A034886(n) - A027868(n). - _Michel Marcus_, Jun 24 2013
%t Array[IntegerLength[#!//.x_/;x~Mod~10==0:>x/10]&,77,0] (* _Giorgos Kalogeropoulos_, Nov 19 2021 *)
%o (Python)
%o from math import factorial
%o def A008906(n): return len(str(factorial(n)).rstrip('0')) # _Chai Wah Wu_, Oct 24 2021
%Y Cf. A027868, A034886.
%K nonn,base,easy
%O 0,5
%A _Russ Cox_
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