OFFSET
0,1
EXAMPLE
For any positive integer n, n! must have at least as many trailing 0's as does (n-1)!; thus, other than the terms where a(n)=0, the sequence is strictly increasing.
2 is the first prime whose factorial (2! = 2) has no trailing 0's, so a(0)=2.
5 is the first prime whose factorial (5! = 120) has one trailing 0, so a(1)=5.
There is no number whose factorial has exactly 5 trailing 0's (since the factorials of 24 and 25 have 4 and 6 trailing 0's, respectively), so a(5)=0.
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Lekraj Beedassy, Nov 02 2010
STATUS
approved