OFFSET
1,1
COMMENTS
The sequence is finite. Proof: Each 6-digit number has at least 4 nonprime substrings. Thus, each number with more than 6 digits has >= 4 nonprime substrings, too. Consequently, there is a boundary b<10^5, such that all numbers > b have more than 3 nonprime substrings.
LINKS
Hieronymus Fischer, Table of n, a(n) for n = 1..310
EXAMPLE
a(1)=10, since 10 has 3 nonprime substrings (0, 1, 10).
a(310)= 73373, since there are 3 nonprime substrings (33, 7337 and 73373).
CROSSREFS
KEYWORD
nonn,fini,base
AUTHOR
Hieronymus Fischer, Aug 26 2012
STATUS
approved