A002971 Numbers k such that 4*k^2 + 25 is prime.

1, 2, 3, 4, 8, 9, 11, 12, 13, 14, 16, 17, 18, 21, 23, 26, 29, 34, 36, 37, 38, 47, 48, 49, 51, 53, 54, 56, 62, 63, 66, 67, 68, 69, 73, 74, 77, 79, 82, 83, 91, 99, 101, 102, 103, 107, 108, 114, 116, 118, 122, 131, 134, 141, 142, 147, 148, 151, 154, 156, 157, 158, 159, 164

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+25)]; // Vincenzo Librandi, Nov 21 2010

Mathematica

Select[Range[200], PrimeQ[4 #^2 + 25] &] (* Vincenzo Librandi, Mar 19 2014 *)

PARI

is(n)=isprime(4*n^2+25) \\ Charles R Greathouse IV, Jun 06 2017