A041044 Numerators of continued fraction convergents to sqrt(28).

5, 16, 37, 127, 1307, 4048, 9403, 32257, 331973, 1028176, 2388325, 8193151, 84319835, 261152656, 606625147, 2081028097, 21416906117, 66331746448, 154080399013, 528572943487, 5439809833883, 16848002445136

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• cofr
• frac
• easy

Links

• Vincenzo Librandi, Table of n, a(n) for n = 0..1000
• Index entries for linear recurrences with constant coefficients, signature (0,0,0,254,0,0,0,-1).

Crossrefs

Cf. A010483, A041045.

Programs

Mathematica

Table[Numerator[FromContinuedFraction[ContinuedFraction[Sqrt[28],n]]],{n,1,50}] (* Vladimir Joseph Stephan Orlovsky, Mar 18 2011 *)
CoefficientList[Series[- (x^7 - 5 x^6 + 16 x^5 - 37 x^4 - 127 x^3 - 37 x^2 - 16 x - 5)/((x^4 - 16 x^2 + 1) (x^4 + 16 x^2 + 1)), {x, 0, 30}], x] (* Vincenzo Librandi, Oct 22 2013 *)

Formula

a(n) = 254*a(n-4)-a(n-8). G.f.: -(x^7-5*x^6+16*x^5-37*x^4-127*x^3-37*x^2-16*x-5)/((x^4-16*x^2+1)*(x^4+16*x^2+1)). [Colin Barker, Jul 16 2012]