

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
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OFFSET

1,1


COMMENTS

Indices where zero occurs in A138479.
For primes in this sequences see A138686.


LINKS



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



KEYWORD

nonn


AUTHOR



STATUS

approved



