A224870 Numbers m such that m^2 + (m+3)^2 is prime.

1, 2, 5, 7, 10, 11, 16, 20, 22, 25, 37, 40, 41, 46, 50, 55, 61, 62, 65, 77, 85, 91, 92, 101, 106, 107, 116, 122, 125, 127, 130, 131, 142, 145, 146, 152, 155, 161, 172, 181, 182, 187, 196, 197, 206, 220, 221, 232, 235, 241, 242, 257, 260, 262, 265, 271, 275, 280, 281, 286, 295, 310, 317, 325, 326, 346, 356, 362, 380, 382, 386, 391

Offset: 1

Author

Zak Seidov, Jul 22 2013

Keywords

• nonn

Links

• Zak Seidov, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A027861, A027862, A076727.

Programs

Maple

A224870:=n->`if`(isprime(n^2 + (n+3)^2), n, NULL): seq(A224870(n), n=1..10^3); # Wesley Ivan Hurt, Feb 11 2017

Mathematica

k = 3; Select[Range[500], PrimeQ[#^2 + (# + k)^2]&]

PARI

isok(n) = isprime(n^2 + (n+3)^2); \\ Michel Marcus, Feb 13 2017

Formula

a(n) = (1/2)*(sqrt(2*A076727(n) - k^2) - k), k = 3.