OFFSET
0,2
COMMENTS
Probably finite sequence. The multiplicative persistence of a number is the number of times you need to multiply the digits together before reaching a single digit.
EXAMPLE
For n=4, a(4) = 39 because 39 is the smallest nonprime number with multiplicative persistence 3: 39 -> 27 -> 14 -> 4.
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Jaroslav Krizek, Oct 23 2011
STATUS
approved