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A042886
Numerators of continued fraction convergents to sqrt(975).
2
31, 125, 281, 1249, 77719, 312125, 701969, 3120001, 194142031, 779688125, 1753518281, 7793761249, 484966715719, 1947660624125, 4380287963969, 19468812480001, 1211446661724031, 4865255459376125, 10941957580476281, 48633085781281249
OFFSET
0,1
FORMULA
G.f.: (31 + 125*x + 281*x^2 + 1249*x^3 + 281*x^4 - 125*x^5 + 31*x^6 - x^7)/(1 - 2498*x^4 + x^8). - Vincenzo Librandi, Dec 08 2013
a(n) = 2498*a(n-4) - a(n-8). - Vincenzo Librandi, Dec 08 2013
MATHEMATICA
Numerator[Convergents[Sqrt[975], 30]] (* or *) CoefficientList[Series[(31 + 125 x + 281 x^2 + 1249 x^3 + 281 x^4 - 125 x^5 + 31 x^6 - x^7)/(1 - 2498 x^4 + x^8), {x, 0, 30}], x] (* Vincenzo Librandi, Dec 08 2013 *)
PROG
(Magma) I:=[31, 125, 281, 1249, 77719, 312125, 701969, 3120001]; [n le 8 select I[n] else 2498*Self(n-4)-Self(n-8): n in [1..30]]; // Vincenzo Librandi, Dec 08 2013
CROSSREFS
Cf. A042887.
Sequence in context: A131992 A042884 A153073 * A042888 A183836 A078656
KEYWORD
nonn,cofr,frac,easy
EXTENSIONS
More terms from Vincenzo Librandi, Dec 08 2013
STATUS
approved