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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
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
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
KEYWORD
nonn,easy
EXTENSIONS
More terms from Jon E. Schoenfield, May 06 2010
STATUS
approved