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A230108
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Values of d such that the equation x^2 - d*y^2 = 2*d has integer solutions.
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1
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2, 3, 6, 8, 11, 12, 18, 19, 22, 24, 27, 32, 38, 43, 44, 48, 50, 51, 54, 59, 66, 67, 72, 75, 76, 83, 86, 88, 96, 98, 99, 102, 107, 108, 114, 118, 123, 128, 131, 134, 139, 146, 147, 150, 152, 162, 163, 166, 171, 172, 176, 178, 179
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OFFSET
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1,1
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LINKS
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EXAMPLE
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43 appears in the sequence because the equation x^2 - 43*y^2 = 86 has integer solutions, such as (x,y) = (387,59).
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MATHEMATICA
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Select[Range[200], FindInstance[x^2-#*y^2==2*#, {x, y}, Integers]!={}&] (* Harvey P. Dale, Jun 22 2019 *)
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PROG
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(PARI) is(n)=sol=bnfisintnorm(bnfinit(z^2-n), 2*n); if(!#sol, 0, p=polcoeff(sol[1], 0); p==floor(p)) \\ Ralf Stephan, Oct 19 2013
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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