A121068 Numbers k such that 8*k^2 + 7 is prime.

0, 3, 27, 30, 33, 48, 57, 60, 72, 75, 78, 108, 117, 123, 135, 150, 162, 192, 198, 207, 228, 243, 270, 300, 303, 312, 342, 345, 390, 408, 417, 423, 435, 480, 498, 507, 510, 513, 543, 552, 555, 573, 618, 633, 642, 645, 657, 675, 705, 723, 732, 738, 747, 750, 780

Offset: 1

Author

Parthasarathy Nambi, Aug 10 2006

Keywords

• nonn
• easy

Comments

All terms are multiples of 3. - Zak Seidov, Aug 11 2006

A201704 is primes of form 8*k^2+7. James C. McMahon, Oct 12 2024

Examples

			If k=135 then 8*k^2 + 7 = 145807 (prime).
		

Crossrefs

Cf. A007522, A201704.

Programs

Magma

[ n: n in [0..1500] | IsPrime(8*n^2 + 7) ]; // Vincenzo Librandi, Jan 31 2011

Maple

a:=proc(n) if isprime(8*n^2+7)=true then n else fi end: seq(a(n),n=0..1000); # Emeric Deutsch, Aug 11 2006

Mathematica

Select[Range[0,780],PrimeQ[8#^2+7]&] (* James C. McMahon, Oct 12 2024 *)

PARI

is(n)=isprime(8*n^2+7) \\ Charles R Greathouse IV, Jun 13 2017

Extensions

More terms from Emeric Deutsch and Joshua Zucker, Aug 11 2006