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 A138685 Numbers n such that there is no prime of the form 2n + p^2 for any prime p. 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; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Indices where zero occurs in A138479. For primes in this sequences see A138686. LINKS Alois P. Heinz, Table of n, a(n) for n = 1..10000 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, 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 Select[Range[400], Mod[#, 3]==1&&CompositeQ[2#+9]&] (* Harvey P. Dale, Feb 23 2017 *) CROSSREFS Cf. A138479, A138686. Sequence in context: A041336 A145417 A157206 * A047724 A046044 A026919 Adjacent sequences: A138682 A138683 A138684 * A138686 A138687 A138688 KEYWORD nonn AUTHOR Artur Jasinski, Mar 26 2008 STATUS approved

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Last modified December 8 14:49 EST 2023. Contains 367680 sequences. (Running on oeis4.)