A139846 - OEIS

A139846

Primes of the form 5x^2 + 21y^2.

5, 41, 89, 101, 269, 461, 509, 521, 761, 881, 929, 941, 1049, 1109, 1181, 1301, 1361, 1601, 1721, 1889, 1949, 2141, 2309, 2441, 2609, 2621, 2729, 2789, 2861, 3041, 3209, 3449, 3461, 3701, 3821, 3881, 3989, 4049, 4241, 4289, 4409, 4721, 4889

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OFFSET

1,1

COMMENTS

Discriminant = -420. See A139827 for more information.

LINKS

Vincenzo Librandi and Ray Chandler, Table of n, a(n) for n = 1..10000 [First 1000 terms from Vincenzo Librandi]

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

FORMULA

The primes are congruent to {5, 41, 89, 101, 209, 269, 341} (mod 420).

MATHEMATICA

QuadPrimes2[5, 0, 21, 10000] (* see A106856 *)

PROG

(Magma) [ p: p in PrimesUpTo(6000) | p mod 420 in {5, 41, 89, 101, 209, 269, 341}]; // Vincenzo Librandi, Jul 29 2012

(PARI) list(lim)=my(v=List([5]), s=[41, 89, 101, 209, 269, 341]); forprime(p=41, lim, if(setsearch(s, p%420), listput(v, p))); Vec(v) \\ Charles R Greathouse IV, Feb 10 2017

CROSSREFS

Sequence in context: A349786 A199692 A031917 * A201718 A142101 A102265

Adjacent sequences: A139843 A139844 A139845 * A139847 A139848 A139849

KEYWORD

nonn,easy

AUTHOR

T. D. Noe, May 02 2008

STATUS

approved