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A041866
Numerators of continued fraction convergents to sqrt(455).
2
21, 64, 2709, 8191, 346731, 1048384, 44378859, 134184961, 5680147221, 17174626624, 727014465429, 2198218022911, 93052171427691, 281354732305984, 11909950928279019, 36011207517143041, 1524380666648286741
OFFSET
0,1
FORMULA
G.f.: -(x^3-21*x^2-64*x-21)/(x^4-128*x^2+1). - Vincenzo Librandi, Nov 11 2013
a(n) = 128*a(n-2)-a(n-4). - Vincenzo Librandi, Nov 11 2013
MATHEMATICA
Numerator[Convergents[Sqrt[455], 30]] (* or *) CoefficientList[Series[-(x^3 - 21 x^2 - 64 x - 21)/(x^4 - 128 x^2 + 1), {x, 0, 25}], x] (* Vincenzo Librandi, Nov 11 2013 *)
PROG
(Magma) I:=[21, 64, 2709, 8191]; [n le 4 select I[n] else 128*Self(n-2)-Self(n-4): n in [1..20]]; // Vincenzo Librandi, Nov 11 2013
CROSSREFS
Cf. A041867.
Sequence in context: A041862 A041860 A041864 * A020211 A014641 A259677
KEYWORD
nonn,cofr,frac,easy,less
AUTHOR
STATUS
approved