A002970 Numbers k such that 4*k^2 + 9 is prime.

1, 4, 5, 10, 16, 19, 20, 26, 29, 31, 35, 41, 44, 49, 50, 55, 56, 59, 70, 71, 80, 85, 94, 95, 100, 101, 106, 109, 110, 121, 149, 154, 160, 166, 175, 179, 184, 190, 191, 200, 205, 206, 211, 224, 236, 241, 245, 251, 256, 265, 269, 271, 284, 286, 289, 299, 304, 314

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn
• easy

References

• E. Kogbetliantz and A. Krikorian, Handbook of First Complex Prime Numbers, Gordon and Breach, NY, 1971, p. 1.
• N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

• T. D. Noe, Table of n, a(n) for n = 1..1000
• E. Kogbetliantz and A. Krikorian Handbook of First Complex Prime Numbers, Gordon and Breach, NY, 1971. [Annotated scans of a few pages]

Programs

Magma

[n: n in [0..600]|IsPrime(4*n^2+9)]; // Vincenzo Librandi, Nov 21 2010

Mathematica

Select[Range[350], PrimeQ[4 #^2 + 9] &] (* Vincenzo Librandi, Mar 19 2014 *)

PARI

is(n)=isprime(4*n^2+9) \\ Charles R Greathouse IV, Feb 17 2017