A002732 Numbers k such that (4*k^2 + 1)/5 is prime. (Formerly M3281 N1324)

4, 6, 11, 14, 21, 24, 26, 29, 31, 39, 44, 46, 51, 54, 76, 79, 89, 94, 99, 101, 111, 119, 124, 129, 131, 136, 146, 149, 154, 156, 164, 176, 179, 181, 194, 201, 211, 214, 229, 231, 239, 244, 246, 254, 261, 279, 286, 294, 301, 311, 314, 319, 326, 331, 346, 349

Offset

1,1

References

L. Euler, De numeris primis valde magnis (E283), reprinted in: Opera Omnia. Teubner, Leipzig, 1911, Series (1), Vol. 3, p. 24.

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

L. Euler, De numeris primis valde magnis (E283), The Euler Archive.

Mathematica

Select[Range[0, 400], PrimeQ[(4 #^2 + 1)/5] &] (* Vincenzo Librandi, Sep 25 2012 *)

Prog

(Magma) [n: n in [4..410] | IsPrime((4*n^2+1) div 5)]; // Vincenzo Librandi, Sep 25 2012
(PARI) is(n)=isprime((4*n^2+1)/5) \\ Charles R Greathouse IV, May 22 2017

Crossrefs

Sequence in context: A096833 A153357 A310591 * A144065 A343098 A036831

Adjacent sequences: A002729 A002730 A002731 * A002733 A002734 A002735

Keyword

nonn,easy

Author

N. J. A. Sloane

Status

approved