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A248220 Values of n such that the equation x^2 - n*y^2 = n*(n+1)*(n+2)/6 has integer solutions. 0
1, 2, 4, 7, 14, 16, 25, 31, 39, 48, 49, 52, 57, 64, 73, 74, 79, 84, 86, 97, 100, 112, 121, 127, 129, 134, 169, 192, 194, 196, 199, 217, 241, 244, 254, 256, 266, 273, 289, 292, 302, 304, 326, 336, 337, 350, 361, 372, 399, 400, 409, 448, 457, 484, 487, 489, 511 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..57.

EXAMPLE

7 is in the sequence because x^2-7*y^2=84 has integer solutions, including (x,y) = (14,4) and (28,10).

MATHEMATICA

Select[Range[300], Length[FullSimplify[Solve[x^2-#*y^2==#*(#+1)*(#+2)/6, {x, y}, Integers]/.C[1]->1]]>0&] (* Vaclav Kotesovec, Oct 05 2014, Mathematica version >= 8 *)

CROSSREFS

Cf. A000292, A134419, A245226, A248194.

Sequence in context: A286371 A030135 A222306 * A018476 A265309 A293825

Adjacent sequences:  A248217 A248218 A248219 * A248221 A248222 A248223

KEYWORD

nonn

AUTHOR

Colin Barker, Oct 04 2014

EXTENSIONS

More terms from Vaclav Kotesovec, Oct 05 2014

STATUS

approved

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Last modified October 22 04:25 EDT 2019. Contains 328315 sequences. (Running on oeis4.)