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A138685
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Numbers n such that there is no prime of the form 2n + p^2 for any prime p.
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10
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13, 28, 34, 43, 55, 58, 67, 73, 76, 88, 97, 100, 103, 106, 118, 133, 139, 145, 148, 157, 160, 163, 166, 178, 181, 184, 193, 199, 202, 208, 214, 223, 232, 238, 244, 253, 259, 262, 265, 268, 271, 283, 286, 298, 301, 307, 310, 313, 328, 331, 340, 343, 349, 352
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OFFSET
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1,1
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COMMENTS
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Indices where zero occurs in A138479.
For primes in this sequences see A138686.
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LINKS
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FORMULA
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Based on comments from Zak Seidov, Don Reble and M. F. Hasler, we now know that these are the numbers n such that n == 1 (mod 3) and 2n + 9 is composite. - N. J. A. Sloane, Apr 20 2008
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MATHEMATICA
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a = {}; Do[p = 0; While[(! PrimeQ[2*n + Prime[p + 1]^2]) && (p < 10000), p++ ]; If[p < 10000, [null], AppendTo[a, n]], {n, 1, 550}]; a
Select[Range[400], Mod[#, 3]==1&&CompositeQ[2#+9]&] (* Harvey P. Dale, Feb 23 2017 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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