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 A002643 Numbers k such that (k^2 + k + 1)/19 is prime. (Formerly M4340 N1817) 1
 7, 11, 26, 45, 83, 125, 140, 182, 197, 201, 216, 239, 258, 311, 330, 353, 444, 467, 482, 486, 524, 539, 558, 600, 752, 771, 843, 881, 885, 923, 980, 999, 1071, 1113, 1170, 1223, 1337, 1356, 1470, 1664, 1835, 1869, 1911, 1949, 1968, 2021, 2078, 2120, 2192 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 REFERENCES A. J. C. Cunningham, Binomial Factorisations, Vols. 1-9, Hodgson, London, 1923-1929; see Vol. 1, pp. 245-259. N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence). N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..1000 A. J. C. Cunningham, Binomial Factorisations, Vols. 1-9, Hodgson, London, 1923-1929. [Annotated scans of a few pages from Volumes 1 and 2] MATHEMATICA Select[Range[2500], PrimeQ[(#^2 + # + 1)/19] &] (* Vincenzo Librandi, Sep 25 2012 *) PROG (PARI) is(n)=isprime((n^2+n+1)/19) \\ Charles R Greathouse IV, Jun 06 2017 CROSSREFS Cf. A002640, A002641, A002642, A002644. Sequence in context: A027830 A134043 A102373 * A276504 A039287 A045222 Adjacent sequences: A002640 A002641 A002642 * A002644 A002645 A002646 KEYWORD nonn,easy AUTHOR N. J. A. Sloane EXTENSIONS More terms from Jon E. Schoenfield, May 06 2010 STATUS approved

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Last modified September 11 16:40 EDT 2024. Contains 375836 sequences. (Running on oeis4.)