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A228554
x-values in the solution to the Pell equation x^2 - 85*y^2 = -1.
2
378, 216041742, 123476065138818, 70571263317093720342, 40334158693601634671687178, 23052504391353119813669652619422, 13175382254784845233371524284127523858, 7530231623112168370599341126488007078134182
OFFSET
1,1
COMMENTS
All terms are multiples of 378.
FORMULA
a(n) = 571538*a(n-1)-a(n-2).
G.f.: 378*x*(x+1) / (x^2-571538*x+1).
MATHEMATICA
LinearRecurrence[{571538, -1}, {378, 216041742}, 20] (* Harvey P. Dale, Jul 10 2019 *)
PROG
(PARI) Vec(378*x*(x+1)/(x^2-571538*x+1) + O(x^30))
CROSSREFS
Cf. A228555 gives the corresponding y-values.
Sequence in context: A171115 A328552 A225994 * A108385 A341188 A020369
KEYWORD
nonn,easy
AUTHOR
Colin Barker, Aug 25 2013
STATUS
approved