

A215685


Smallest prime whose decimal expansion consists of the concatenation of a 2digit emirp, a 3digit emirp, a 4digit emirp, ..., and an ndigit emirp (A006567).


0



13, 13337, 131071021, 13107100910711, 13107100910007100483, 131071009100071000491000187, 13107100910007100049100003310000657, 13107100910007100049100003310000169100007543, 131071009100071000491000033100001691000000071000015351
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OFFSET

2,1


COMMENTS

If a(n) exists it has A000217(n)1 digits.


LINKS



EXAMPLE

a(2) = 13 which is a prime, and whose decimal digits reversed, 31, is also a prime.
a(3) = 13337, which is a prime, and the concatenation of 13 (an emirp) and 337 (an emirp because 733 is also a prime). It happens that the digital reversal of a(3), 73331, is also prime, so that 13337 is an emirp, but that is not a requirement for this sequence.
Note that a(4) is a prime but not an emirp, because 12070131 = 3 * 61 * 65957.


CROSSREFS



KEYWORD

nonn,base,easy


AUTHOR



EXTENSIONS



STATUS

approved



