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 A121259 Numbers n such that (3n^2+1)/4 is prime. 1
 3, 5, 7, 9, 13, 19, 21, 23, 27, 29, 35, 47, 49, 51, 55, 57, 61, 65, 69, 75, 77, 83, 85, 91, 97, 99, 105, 111, 117, 125, 127, 133, 135, 149, 161, 163, 173, 177, 181, 183, 187, 191, 211, 217, 239, 247, 251, 257, 259, 273, 281, 285, 295, 307, 313, 315, 317, 329, 331, 341 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS FORMULA a(n)=(4*A002407(n)-1)/3 MATHEMATICA Select[Range[400], PrimeQ[(3#^2+1)/4]&]  (* Harvey P. Dale, Mar 24 2011 *) PROG (PARI) is(n)=isprime((3*n^2+1)/4) \\ Charles R Greathouse IV, Jun 13 2017 CROSSREFS Cf. comment by Michael Somos in A002407. Sequence in context: A200975 A058871 A126278 * A211139 A089228 A262602 Adjacent sequences:  A121256 A121257 A121258 * A121260 A121261 A121262 KEYWORD nonn,easy AUTHOR Zak Seidov, Aug 23 2006 STATUS approved

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Last modified July 28 00:54 EDT 2021. Contains 346316 sequences. (Running on oeis4.)