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A041775
Denominators of continued fraction convergents to sqrt(408).
2
1, 5, 201, 1010, 40601, 204015, 8201201, 41210020, 1656602001, 8324220025, 334625403001, 1681451235030, 67592674804201, 339644825256035, 13653385685045601, 68606573250484040, 2757916315704407201, 13858188151772520045, 557085442386605209001
OFFSET
0,2
FORMULA
G.f.: -(x^2-5*x-1) / (x^4-202*x^2+1). - Colin Barker, Nov 24 2013
a(n) = 202*a(n-2) - a(n-4). for n>3. - Vincenzo Librandi, Dec 24 2013
MATHEMATICA
Denominator[Convergents[Sqrt[408], 30]] (* Vincenzo Librandi, Dec 24 2013 *)
PROG
(Magma) I:=[1, 5, 201, 1010]; [n le 4 select I[n] else 202*Self(n-2)-Self(n-4): n in [1..40]]; // Vincenzo Librandi, Dec 24 2013
CROSSREFS
Sequence in context: A128791 A303136 A244848 * A093976 A337579 A196799
KEYWORD
nonn,frac,easy
AUTHOR
EXTENSIONS
More terms from Colin Barker, Nov 24 2013
STATUS
approved