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A086474
a(1) = 4 and then least composite such that every partial concatenation of 2 or more terms is a prime.
0
4, 21, 39, 49, 93, 99, 143, 183, 207, 231, 247, 261, 267, 531, 533, 549, 889, 999, 1167, 1641, 1701, 1809, 2019, 2327, 2349, 2469, 2553, 3043, 3093, 3123, 3159, 3639, 3857, 3937, 4197, 4221, 4233, 4323, 5271, 5369, 5611, 5661, 6641, 7599, 7819, 8021, 8043
OFFSET
1,1
EXAMPLE
421,42139 etc. are primes.
CROSSREFS
Sequence in context: A161444 A188219 A280091 * A085703 A063122 A110737
KEYWORD
base,nonn
AUTHOR
Amarnath Murthy and Jason Earls, Jul 22 2003
STATUS
approved