A002643 Numbers k such that (k^2 + k + 1)/19 is prime. (Formerly M4340 N1817)

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

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