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A138685 Numbers n such that there is no prime of the form 2n + p^2 for any prime p. +0
10
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)
OFFSET

1,1

COMMENT

Indices where zero occurs in A138479

For primes in this sequences see A138686

FORMULA

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

MATHEMATICA

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

CROSSREFS

Cf. A138479, A138686.

Sequence in context: A145417 A157206 A101215 this_sequence A047724 A046044 A026919

Adjacent sequences: A138682 A138683 A138684 this_sequence A138686 A138687 A138688

KEYWORD

nonn

AUTHOR

Artur Jasinski (grafix(AT)csl.pl), Mar 26 2008

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Last modified November 25 20:09 EST 2009. Contains 167514 sequences.


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