A222963 a(n) = (p-3)*(p+3)/4 where p is the n-th prime.

0, 4, 10, 28, 40, 70, 88, 130, 208, 238, 340, 418, 460, 550, 700, 868, 928, 1120, 1258, 1330, 1558, 1720, 1978, 2350, 2548, 2650, 2860, 2968, 3190, 4030, 4288, 4690, 4828, 5548, 5698, 6160, 6640, 6970, 7480, 8008, 8188

Offset: 2

Author

Vincenzo Librandi, Apr 05 2013

Keywords

• nonn
• easy

Comments

Old name was: Numbers n such that sqrt(4*n+9) is prime.

Links

• Vincenzo Librandi, Table of n, a(n) for n = 2..1000

Crossrefs

Subsequence of A028552.

Cf. A000040, A001248, A005097, A168669.

Programs

Magma

[(p^2-9)/4: p in PrimesInInterval(3, 200)];

Mathematica

Select[Range[0, 10000], PrimeQ[Sqrt[4 # + 9]]&]

Formula

4*a(n)+9 = A001248(n).

a(n) = A166011(n)/2. - Michel Marcus, Apr 22 2016