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A195559 Denominators a(n) of Pythagorean approximations b(n)/a(n) to 2/3. 4
1, 4, 91, 240, 840, 989, 5396, 117719, 312120, 1089720, 1284121, 7003804, 152799571, 405130920, 1414456320, 1666787669, 9090932396, 198333725039, 525859622640, 1835963213040, 2163489110641, 11800023246004, 257437022301451 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

See A195500 for a discussion and references.

LINKS

Table of n, a(n) for n=1..23.

MATHEMATICA

r = 2/3; z = 25;

p[{f_, n_}] := (#1[[2]]/#1[[

1]] &)[({2 #1[[1]] #1[[2]], #1[[1]]^2 - #1[[

2]]^2} &)[({Numerator[#1], Denominator[#1]} &)[

Array[FromContinuedFraction[

ContinuedFraction[(#1 + Sqrt[1 + #1^2] &)[f], #1]] &, {n}]]]];

{a, b} = ({Denominator[#1], Numerator[#1]} &)[

p[{r, z}]] (* A195559, A195560 *)

Sqrt[a^2 + b^2] (* A195561 *)

(* Peter J. C. Moses, Sep 02 2011 *)

CROSSREFS

Cf. A195500, A195560, A195561.

Sequence in context: A146506 A202575 A201721 * A195551 A024261 A337827

Adjacent sequences: A195556 A195557 A195558 * A195560 A195561 A195562

KEYWORD

nonn

AUTHOR

Clark Kimberling, Sep 21 2011

STATUS

approved

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Last modified February 6 23:12 EST 2023. Contains 360111 sequences. (Running on oeis4.)