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A041022 Numerators of continued fraction convergents to sqrt(15). 2
3, 4, 27, 31, 213, 244, 1677, 1921, 13203, 15124, 103947, 119071, 818373, 937444, 6443037, 7380481, 50725923, 58106404, 399364347, 457470751, 3144188853, 3601659604, 24754146477, 28355806081 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,1
LINKS
FORMULA
G.f.: (3+4*x+3*x^2-x^3)/(1-8*x^2+x^4).
From Gerry Martens, Jul 11 2015: (Start)
Interspersion of 2 sequences [a0(n),a1(n)] for n>0:
a0(n) = (-((4-sqrt(15))^n*(3+sqrt(15)))+(-3+sqrt(15))*(4+sqrt(15))^n)/2.
a1(n) = ((4-sqrt(15))^n+(4+sqrt(15))^n)/2. (End)
MATHEMATICA
Table[Numerator[FromContinuedFraction[ContinuedFraction[Sqrt[15], n]]], {n, 1, 50}] (* Vladimir Joseph Stephan Orlovsky, Mar 17 2011 *)
Numerator[Convergents[Sqrt[15], 30]] (* Vincenzo Librandi, Oct 28 2013 *)
a0[n_] := (-((4-Sqrt[15])^n*(3+Sqrt[15]))+(-3+Sqrt[15])*(4+Sqrt[15])^n)/2 // Simplify
a1[n_] := ((4-Sqrt[15])^n+(4+Sqrt[15])^n)/2 // Simplify
Flatten[MapIndexed[{a0[#], a1[#]} &, Range[20]]] (* Gerry Martens, Jul 11 2015 *)
CROSSREFS
Sequence in context: A222112 A032832 A041021 * A157163 A042225 A094084
KEYWORD
nonn,cofr,frac,easy
AUTHOR
STATUS
approved

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Last modified July 20 15:17 EDT 2024. Contains 374459 sequences. (Running on oeis4.)