A356739 a(n) is the smallest k such that k! has at least n consecutive zeros immediately after the leading digit in base 10.

7, 153, 197, 7399, 24434, 24434, 9242360, 238861211, 238861211

Offset: 1

Author

Christian Perfect, Aug 25 2022

Keywords

• nonn
• base
• more

Examples

			a(1) = 7, because 7! = 5040 has one zero immediately after the leading digit, and there is no k<7 with that property.
		

Crossrefs

Cf. A000142, A027869.

Programs

Python

from itertools import count
t = 1
n = 1
for k in count(1):
    t *= k
    while str(t)[1:1+n] == '0'*n:
        print(n,k)
        n += 1

Extensions

a(5)-a(6) from Amiram Eldar, Aug 25 2022

a(7)-a(9) from Jinyuan Wang, Aug 25 2022