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A109445
Numbers n such that (concatenation of even integers through n) - 1 is a prime.
0
4, 8, 10, 42, 452, 1014
OFFSET
1,1
COMMENTS
Next term is greater than 2000. All terms less than 1000 correspond to certified primes (Primo 2.2.0 beta).
EXAMPLE
4 is a term because 24 - 1 = 23 is prime.
8 is a term because 2468 - 1 = 2467 is prime.
MATHEMATICA
p = ""; Do[p = p <> ToString[2*n]; If[PrimeQ[ToExpression[p] - 1], Print[2*n]], {n, 1, 10^3}]
CROSSREFS
Cf. A066811.
Sequence in context: A323151 A037004 A136861 * A316505 A293597 A131803
KEYWORD
base,nonn
AUTHOR
Ryan Propper, Aug 26 2005
STATUS
approved