

A077391


Smallest ndigit prime which leaves a prime at every step if most significant digit and least significant digit are deleted until a one digit or two digit prime is obtained, or 0 if no such prime exists.


0



2, 11, 127, 1021, 10313, 100237, 1002931, 10002331, 100023331, 1000023337, 10000239937, 100000233397, 1000002339937, 10000002339931, 100000139991331, 1000000023399331, 10000000233993397, 100000000293999997
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OFFSET

1,1


COMMENTS

Conjecture: No term is zero.


LINKS



EXAMPLE

a(6) = 100237: this is the smallest 6digit number such that deleting MSD and LSD yields prime at every step, i.e. 100237, 0023, 02 all are primes.


CROSSREFS



KEYWORD

base,nonn


AUTHOR



EXTENSIONS



STATUS

approved



