cp's OEIS Frontend

A356861 a(n) is the number of nonzero digits in the product of the first n numbers not divisible by 5.

%I A356861 #7 Sep 04 2022 12:38:51
%S A356861 1,1,1,1,2,3,2,3,5,6,5,8,10,10,11,12,15,14,16,19,20,20,19,23,24,25,27,
%T A356861 24,27,31,32,32,34,38,36,40,41,40,44,47,43,50,52,53,50,51,56,61,60,58,
%U A356861 63,61,64,67,72,67,70,72,76,72,78,84,83,85,84,90,91,91,90
%N A356861 a(n) is the number of nonzero digits in the product of the first n numbers not divisible by 5.
%F A356861 a(n) = A055640(A356858(n)).
%t A356861 Table[Length[Select[IntegerDigits[Product[Floor[(5i-1)/4], {i,n}]], Positive]], {n,0,68}]
%o A356861 (Python)
%o A356861 from math import prod
%o A356861 def a(n): s = str(prod((5*k-1)//4 for k in range(1, n+1))); return len(s) - s.count("0")
%o A356861 print([a(n) for n in range(69)]) # _Michael S. Branicky_, Sep 01 2022
%Y A356861 Cf. A047201, A055640, A356858.
%Y A356861 Cf. A356859 (number of zero digits), A356860 (number of digits).
%K A356861 nonn,base
%O A356861 0,5
%A A356861 _Stefano Spezia_, Sep 01 2022