A244031 Integers n>1 such that the quadratic form x^2+n*y^2 does not represent a prime strictly between n and 2n.

3, 5, 8, 11, 17, 23, 24, 26, 29, 35, 41, 56, 59, 68, 83, 89, 107, 119, 120, 125, 134, 179, 185, 194, 206, 251, 263, 269, 290, 293, 314, 326, 341, 356, 371, 389, 401, 404, 461, 464, 479, 489, 491, 524, 545, 569, 593, 626

Offset

1,1

Comments

Or: Positive numbers n such that n + k^2 is composite for all 1 <= k^2 <= n.

The next term a(105), if it exists, is > 156*10^6. - M. F. Hasler, May 07 2018

Links

N. J. A. Sloane, Table of n, a(n) for n = 1..104 (cf. Jagy & Kaplansky).

William C. Jagy and Irving Kaplansky, Positive definite binary quadratic forms that represent the same primes [Cached copy]

Prog

(PARI) is(n)=!for(k=1, sqrtint(n), isprime(n+k^2)&&return) \\ M. F. Hasler, May 07 2018

Crossrefs

Union of A244029 (subsequence of primes) and A244030 (composite terms).

Sequence in context: A281333 A371154 A338204 * A194803 A284835 A308266

Adjacent sequences: A244028 A244029 A244030 * A244032 A244033 A244034

Keyword

nonn

Author

N. J. A. Sloane, Jun 22 2014

Extensions

Added "n>1" as suggested by David J. Seal. - N. J. A. Sloane, May 19 2018

Status

approved