cp's OEIS Frontend

A356859 a(n) is the number of zero digits in the product of the first n numbers not divisible by 5.

%I A356859 #6 Sep 04 2022 12:38:30
%S A356859 0,0,0,0,0,0,2,1,0,0,2,1,0,1,1,1,0,2,1,0,0,2,4,1,2,2,2,6,5,2,3,5,4,2,
%T A356859 5,3,4,6,4,3,8,3,3,4,8,9,6,3,5,9,6,10,9,7,4,11,10,10,8,13,9,5,8,8,11,
%U A356859 7,8,10,13,11,10,12,11,13,13,16,6,16,10,21,17
%N A356859 a(n) is the number of zero digits in the product of the first n numbers not divisible by 5.
%F A356859 a(n) = A055641(A356858(n)).
%t A356859 Table[Count[IntegerDigits[Product[Floor[(5i-1)/4], {i,n}]], 0], {n,0,80}]
%o A356859 (Python)
%o A356859 from math import prod
%o A356859 def a(n): return str(prod((5*k-1)//4 for k in range(1, n+1))).count("0")
%o A356859 print([a(n) for n in range(81)]) # _Michael S. Branicky_, Sep 01 2022
%Y A356859 Cf. A047201, A055641, A356858.
%Y A356859 Cf. A356860 (number of digits), A356861 (number of nonzero digits).
%K A356859 nonn,base
%O A356859 0,7
%A A356859 _Stefano Spezia_, Sep 01 2022