A154742 Denominators of the convergents of the continued fraction for sqrt{1 - 1/sqrt{2}}, the abscissa of the point of bisection of the arc of the unit lemniscate (x^2 + y^2)^2 = x^2 - y^2 in the first quadrant.

1, 0, 1, 1, 2, 11, 13, 24, 85, 534, 619, 2391, 7792, 80311, 810902, 891213, 1702115, 2593328, 14668755, 31930838, 110461269, 142392107, 252853376, 900952235, 5658566786, 6559519021, 58134718954, 4308528721617, 8675192162188

Offset

-2,5

Links

G. C. Greubel, Table of n, a(n) for n = -2..1000

Example

sqrt{1 - 1/sqrt{2}} = 0.541196100146196984399723205366... = [0; 1, 1, 5, 1, 1, 3, 6, 1, 3, 3, 10, 10, ...], the convergents of which are 0/1, 1/0, [0/1], 1/1, 1/2, 6/11, 7/13, 13/24, 46/85, 289/534, 335/619, 1294/2391, 4217/7792, ..., with brackets marking index 0. Those prior to index 0 are for initializing the recurrence.

Mathematica

nmax = 100; cfrac = ContinuedFraction[ Sqrt[ 1 - 1/Sqrt[2] ], nmax + 1]; Join[ {1, 0}, Denominator[ Table[ FromContinuedFraction[ Take[cfrac, j] ], {j, 1, nmax + 1} ] ] ]

Crossrefs

Cf. A154739, A154740 and A154741 for the decimal expansion, the continued fraction and the numerators of the convergents.

Sequence in context: A042453 A041885 A247338 * A257329 A063587 A038972

Adjacent sequences: A154739 A154740 A154741 * A154743 A154744 A154745

Keyword

nonn,frac,easy

Author

Stuart Clary, Jan 14 2009

Status

approved