

A090559


Beginning with 2, least number such that concatenation of r copies of a(r), r = 1 to n is prime.


1



2, 1, 3, 1, 9, 3, 273, 219, 7, 281, 11, 119, 1019, 111, 47, 69, 171, 161, 103, 477, 817, 129, 271, 73, 1867, 381, 507, 113, 2643, 487, 3037, 727, 1109, 1789, 5829, 4937, 767, 12809, 1979, 587, 8417, 1623, 7233, 9079, 6739, 2269, 10251, 8911, 27881, 2691, 5257
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OFFSET

1,1


COMMENTS

For n > 1, a(n) is odd and a(n) != 5 mod 10.  Chai Wah Wu, Jun 17 2019


LINKS

Table of n, a(n) for n=1..51.


EXAMPLE

2,211,211333,2113331111,211333111199999 are all prime.


CROSSREFS

Cf. A090560.
Sequence in context: A185176 A198315 A126761 * A186725 A301935 A237978
Adjacent sequences: A090556 A090557 A090558 * A090560 A090561 A090562


KEYWORD

base,more,nonn


AUTHOR

Amarnath Murthy, Dec 10 2003


EXTENSIONS

More terms from Max Alekseyev, Sep 04 2009
a(38)a(51) from Chai Wah Wu, Jun 17 2019


STATUS

approved



