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A040002 Continued fraction for sqrt(5). 12
2, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4 (list; constant; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

Decimal expansion of 11/45. - Natan Arie Consigli, Jan 19 2016

LINKS

Harry J. Smith, Table of n, a(n) for n = 0..20000

G. Xiao, Contfrac

Index entries for continued fractions for constants

Index of eventually constant sequences

Index of divisibility sequences

FORMULA

a(n) = 4 - 2*(binomial(2*n,n) mod 2), with n>=0. - Paolo P. Lava, Jun 11 2009

a(0) = 2, a(n) = 4 n>0. - Natan Arie Consigli, Jan 19 2016

EXAMPLE

2.236067977499789696409173668... = 2 + 1/(4 + 1/(4 + 1/(4 + 1/(4 + ...)))). - Harry J. Smith, Jun 01 2009

MAPLE

Digits := 100: convert(evalf(sqrt(N)), confrac, 90, 'cvgts'):

MATHEMATICA

ContinuedFraction[Sqrt[5], 300] (* Vladimir Joseph Stephan Orlovsky, Mar 04 2011 *)

PadRight[{2}, 120, {4}] (* Harvey P. Dale, Jul 06 2019 *)

PROG

(PARI) { allocatemem(932245000); default(realprecision, 26000); x=contfrac(sqrt(5)); for (n=0, 20000, write("b040002.txt", n, " ", x[n+1])); } \\ Harry J. Smith, Jun 01 2009

CROSSREFS

Cf. A002163 Decimal expansion.

Continued fraction for sqrt(a²+1) = (a, 2a, 2a, 2a....): A040000 (contfrac(sqrt(2)) = (1,2,2,...)), A040002, A040006, A040012, A040020, A040030, A040042, A040056, A040072, A040090, A040110 (contfrac(sqrt(122)) = (11,22,22,...)), A040132, A040156, A040182, A040210, A040240, A040272, A040306, A040342, A040380, A040420 (contfrac(sqrt(442)) = (21,42,42,...)), A040462, A040506, A040552, A040600, A040650, A040702, A040756, A040812, A040870, A040930 (contfrac(sqrt(962)) = (31,62,62,...)).

Sequence in context: A036264 A105192 A203638 * A151798 A334897 A035684

Adjacent sequences:  A039999 A040000 A040001 * A040003 A040004 A040005

KEYWORD

nonn,cofr,easy,cons

AUTHOR

N. J. A. Sloane

STATUS

approved

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Last modified August 12 01:37 EDT 2020. Contains 336434 sequences. (Running on oeis4.)