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Search: id:A138685
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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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+0
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
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Indices where zero occurs in A138479
For primes in this sequences see A138686
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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 (njas(AT)research.att.com), 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
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CROSSREFS
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Cf. A138479, A138686.
Sequence in context: A145417 A157206 A101215 this_sequence A047724 A046044 A026919
Adjacent sequences: A138682 A138683 A138684 this_sequence A138686 A138687 A138688
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KEYWORD
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nonn
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AUTHOR
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Artur Jasinski (grafix(AT)csl.pl), Mar 26 2008
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