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A089726
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Smallest prime of the form nk+1, k > n.
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2
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3, 7, 13, 29, 31, 43, 71, 73, 109, 131, 199, 157, 313, 211, 241, 337, 307, 379, 419, 421, 463, 617, 599, 601, 701, 859, 757, 953, 929, 991, 1117, 1153, 1123, 1259, 1471, 1549, 1481, 1483, 1873, 1721, 1723, 1933, 1979, 2069, 2161, 2347, 2351, 2593, 2549, 2551
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OFFSET
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1,1
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LINKS
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EXAMPLE
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a(7)=71 because 7*10+1=71 is prime, whereas 7*8+1=57 and 7*9+1=64 are composite.
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MATHEMATICA
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f[n_] := Block[{k = n + 1}, While[ !PrimeQ[k*n + 1], k++ ]; k*n + 1]; Array[f, 50] (* Robert G. Wilson v, Dec 17 2009 *)
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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