A281295 Primes which cannot be written as x^2 + 11*y^2, where x, y > 0.

2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 167, 173, 179, 181, 191, 193, 197, 211, 223, 227, 229, 233, 239, 241, 251, 263, 271, 277, 281, 283, 293, 307, 313, 317

Offset: 1

Author

Arkadiusz Wesolowski, Jan 19 2017

Keywords

• nonn

Comments

Integers n that cannot be expressed as the product of two numbers of the form a + b*sqrt(-11), where a > 0 and b >= 0 (excluding 1 and n).

Crossrefs

Cf. A033209.

Programs

Magma

Sort([11] cat [p: p in PrimesUpTo(317) | NormEquation(11, p) eq false]);

Formula

a(n) ~ 6/5 * n log n.