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A174751
x-values in the solution to x^2-39*y^2=1.
2
1, 25, 1249, 62425, 3120001, 155937625, 7793761249, 389532124825, 19468812480001, 973051091875225, 48633085781281249, 2430681237972187225, 121485428812828080001, 6071840759403431812825, 303470552541358762561249
OFFSET
1,2
COMMENTS
The corresponding values of y of this Pell equation are in A174776.
FORMULA
a(n) = 50*a(n-1)-a(n-2) with a(1)=1, a(2)=25.
G.f.: x*(1-25*x)/(1-50*x+x^2).
MATHEMATICA
LinearRecurrence[{50, -1}, {1, 25}, 30]
Rest[CoefficientList[Series[x (1-25x)/(1-50x+x^2), {x, 0, 20}], x]] (* Harvey P. Dale, Aug 10 2021 *)
PROG
(Magma) I:=[1, 25]; [n le 2 select I[n] else 50*Self(n-1)-Self(n-2): n in [1..20]];
CROSSREFS
Cf. A174776.
Sequence in context: A012851 A181719 A096330 * A042203 A042200 A104593
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Apr 13 2010
STATUS
approved