

A088115


a(n) = largest prime using least number of possible digits with a digit sum n, or 0 if no such number exists. E.g., if n > 9 and there are no twodigit primes with a given digit sum n then threedigit numbers are explored and so on.


0



0, 2, 3, 31, 5, 0, 7, 71, 0, 73, 83, 0, 67, 59, 0, 97, 89, 0, 991, 983, 0, 967, 977, 0, 997, 9791, 0, 9973, 9929, 0, 9967, 9887, 0, 99961, 8999, 0, 99991, 99929, 0, 99877, 99689, 0, 98899, 99989, 0, 999883, 999983, 0, 999769, 999959, 0, 999979, 989999, 0
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,2


COMMENTS

a(26) = 9719 as both 989 and 899 are composite. This is the first genuine case in which the number of digits used is more than floor(n/9) + 1 (after singledigit composite even numbers 4 and 8).


LINKS



EXAMPLE

a(7) = 7.
a(8) = 71 as 8 is not a prime.


CROSSREFS



KEYWORD

base,nonn


AUTHOR



EXTENSIONS



STATUS

approved



