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A230108 Values of d such that the equation x^2 - d*y^2 = 2*d has integer solutions. 1
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..53.

EXAMPLE

43 appears in the sequence because the equation x^2 - 43*y^2 = 86 has integer solutions, such as (x,y) = (387,59).

MATHEMATICA

Select[Range[200], FindInstance[x^2-#*y^2==2*#, {x, y}, Integers]!={}&] (* Harvey P. Dale, Jun 22 2019 *)

PROG

(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

CROSSREFS

Cf. A172000, A230109.

Sequence in context: A020489 A002240 A099798 * A097383 A072893 A127758

Adjacent sequences:  A230105 A230106 A230107 * A230109 A230110 A230111

KEYWORD

nonn

AUTHOR

Colin Barker, Oct 09 2013

STATUS

approved

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Last modified December 5 00:21 EST 2021. Contains 349530 sequences. (Running on oeis4.)