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A141166
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Primes of the form x^2+15*x*y-y^2.
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8
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37, 53, 173, 193, 229, 241, 347, 359, 383, 439, 443, 449, 461, 503, 509, 541, 593, 607, 617, 619, 643, 691, 907, 967, 977, 1019, 1051, 1063, 1097, 1109, 1249, 1277, 1291, 1303, 1321, 1399, 1429, 1583, 1667, 1741, 1783, 1993, 1997, 2003, 2087, 2137, 2143, 2333, 2347, 2351
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OFFSET
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1,1
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COMMENTS
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Discriminant = 229. Class = 3. Binary quadratic forms a*x^2+b*x*y+c*y^2 have discriminant d = b^2-4ac. They can represent primes only if gcd(a,b,c)=1. [Edited by M. F. Hasler, Jan 27 2016]
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REFERENCES
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Z. I. Borevich and I. R. Shafarevich, Number Theory
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LINKS
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EXAMPLE
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a(2)=53 because we can write 53= 3^2+15*3*1-1^2
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MATHEMATICA
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lim = 100; Rest@ Union@ Abs@ Flatten@ Table[x^2 + 15 x y - y^2, {x, lim}, {y, lim}] /. n_ /; CompositeQ@ n -> Nothing (* Michael De Vlieger, Jan 27 2016 *)
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PROG
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(PARI) is_A141166(p)=qfbsolve(Qfb(1, 15, -1), p) \\ Returns nonzero (actually, a solution [x, y]) iff p is a member of the sequence. For efficiency it is assumed that p is prime. Example usage: select(is_A141166, primes(500)) - M. F. Hasler, Jan 27 2016
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CROSSREFS
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For a list of sequences giving numbers and/or primes represented by binary quadratic forms, see the "Binary Quadratic Forms and OEIS" link.
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KEYWORD
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nonn
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AUTHOR
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Laura Caballero Fernandez, Lourdes Calvo Moguer, Maria Josefa Cano Marquez, Oscar Jesus Falcon Ganfornina and Sergio Garrido Morales (sergarmor(AT)yahoo.es), Jun 12 2008
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STATUS
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approved
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