OFFSET
1,3
COMMENTS
Either all digits are '1', or one of the digits can be a prime (2, 3, 5, 7).
The initial 0 is included by convention. (Some authors consider that the decimal expansion of 0 is the empty sum (0 has no digits) whence the product of digits is 1.)
PROG
CROSSREFS
KEYWORD
nonn,base
AUTHOR
M. F. Hasler, Apr 23 2019
STATUS
approved