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A088212
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Smallest k>1 such that n+k^2 is prime.
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2
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2, 3, 2, 3, 6, 5, 2, 3, 2, 3, 6, 5, 2, 3, 2, 5, 6, 5, 2, 3, 4, 3, 6, 7, 2, 9, 2, 3, 12, 7, 4, 3, 2, 3, 6, 5, 2, 3, 2, 7, 24, 5, 2, 3, 4, 5, 6, 5, 2, 3, 4, 3, 6, 5, 2, 9, 2, 3, 18, 7, 6, 3, 2, 3, 6, 25, 2, 9, 2, 3, 6, 5, 4, 3, 2, 5, 6, 5, 2, 3, 4, 5, 12, 5, 2, 9, 4, 3, 12, 7, 4, 3, 2, 3, 6, 19, 2, 3, 2, 3, 6, 5, 2
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OFFSET
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1,1
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COMMENTS
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Conjecture: all integers >1 eventually appear. Among first 300000 terms, first absent integers are 113, 119, 122, 124, 127, 130, 134, 136, 137, 139, 140, 142, 143, 145, 146, 148, 149, 151, 152, 154, 155, 157, 158, 160, 161, 163, 164, 166, 167, 169, 170, 172, 173, 175, 176, 178, 179, 181, 182, 184, 185, 186, 187, 188, 190, 191, 193, 194, 196, 197, 199, 200. - Zak Seidov, Jun 06 2013
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LINKS
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EXAMPLE
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n=1: 1+2^2=5; n=5: 5+6^2=41.
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MATHEMATICA
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k[n_]:=Module[{k=2}, While[!PrimeQ[n+k^2], k++]; k]; Array[k, 110] (* Harvey P. Dale, Aug 19 2011 *)
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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