A106917 Primes of the form 2x^2 + 7y^2.
2, 7, 71, 79, 113, 191, 193, 263, 337, 401, 457, 463, 569, 599, 617, 631, 641, 809, 823, 863, 919, 991, 1009, 1031, 1201, 1289, 1297, 1327, 1367, 1471, 1583, 1607, 1801, 1831, 1913, 1999, 2087, 2111, 2143, 2153, 2297, 2311, 2473, 2521, 2543
Offset: 1
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)
Programs
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Mathematica
QuadPrimes2[2, 0, 7, 10000] (* see A106856 *)
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PARI
list(lim)=my(v=List(),w,t); for(x=0, sqrtint(lim\2), w=2*x^2; for(y=0, sqrtint((lim-w)\7), if(isprime(t=w+7*y^2), listput(v,t)))); Set(v) \\ Charles R Greathouse IV, Feb 09 2017
Comments