1,1

Also primes of the form x^2 + 120y^2. - T. D. Noe, Apr 29 2008

Also primes of the form x^2+240y^2. See A140633. - T. D. Noe, May 19 2008

In base 12, the sequence is 181, 2X1, 421, 541, 701, 7X1, 841, 881, 921, X41, E21, 1061, 1261, 1301, 13X1, 1561, 1681, 18X1, 1921, 1981, 1X01, 1E41, 2061, 2221, 2301, 2481, 2521, 26X1, 2781, 28X1, 2941, 2X61, 3021, 3081, 31X1, 3241, 3281, 3321, 3361, 34X1, 3661, 3821, 3901, where X is 10 and E is 11. Moreover, the discriminant is 340. - Walter Kehowski, Jun 01 2008

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

N. J. A. Sloane et al., Binary Quadratic Forms and OEIS (Index to related sequences, programs, references)

The primes are congruent to {1, 49} (mod 120). - T. D. Noe, Apr 29 2008 [This is a necessary and sufficient condition since the discriminant -480 is a term in A003171 (i.e., there is 1 class of binary quadratic forms per genus for discriminant -480), so the primes represented by any binary quadratic form are determined by a congruence condition. - Jianing Song, Jan 06 2026]

QuadPrimes2[1, 0, 120, 10000] (* see A106856 *)

(Magma) [ p: p in PrimesUpTo(7000) | p mod 120 in {1, 49}]; // Vincenzo Librandi, Jul 28 2012

Cf. A139489, A007645, A068228, A007519, A033212, A033212, A107152, A107008, A033215, A107145, A139490, A139491.

Cf. A139643.

Sequence in context: A376501 A050968 A142918 * A140629 A325088 A321582

Adjacent sequences: A139499 A139500 A139501 * A139503 A139504 A139505

nonn,easy

Artur Jasinski, Apr 24 2008

approved