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A260880
Smallest k such that 1000...0//k (concatenation of 10^n and k) is prime.
1
1, 1, 9, 7, 3, 3, 37, 7, 7, 19, 3, 37, 31, 37, 61, 13, 3, 3, 39, 139, 57, 9, 49, 7, 67, 331, 319, 211, 57, 33, 49, 61, 103, 69, 67, 43, 321, 37, 3, 169, 63, 57, 31, 121, 9, 33, 217, 69, 9, 327, 171, 157, 31, 21, 279, 3, 193, 19, 67, 7, 121, 399, 57, 49, 49, 49
OFFSET
0,3
LINKS
EXAMPLE
The smallest prime whose decimal expansion starts with 10^6 = 1000000 is 100000037, so a(6) = 37.
PROG
(PARI) a(n) = my(k=1); while(!ispseudoprime(eval(Str(10^n, k))), k++); k
CROSSREFS
Similar to but different from A033873.
Sequence in context: A363766 A251734 A033873 * A135449 A060388 A081821
KEYWORD
nonn,base
AUTHOR
Felix Fröhlich, Aug 02 2015
STATUS
approved