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A059926 Quotient cycle length in continued fraction expansion of sqrt(2^n+1). +0
4
1, 4, 1, 10, 1, 16, 1, 44, 1, 74, 1, 46, 1, 204, 1, 714, 1, 702, 1, 908, 1, 404, 1, 7754, 1, 1136, 1, 9886, 1, 8154, 1, 23578, 1, 65096, 1, 404762, 1, 23992, 1, 3514774, 1, 110124, 1, 4802160, 1, 6490450, 1, 180832, 1, 115972, 1, 770304, 1, 62665998 (list; graph; listen)
OFFSET

4,2

COMMENT

For n=1,2 a(1)=2, a(2)=1; for n=3 it is not a quadratic surd.

EXAMPLE

For n=7 and n=8 the periods after the transient are as follows: cfrac(sqrt(2^7+1),'periodic','quotients'); gives [[11], [2, 1, 3, 1, 6, 1, 3, 1, 2, 22]] cfrac(sqrt(2^8+1),'periodic','quotients'); gives [[16], [32]]

MAPLE

with(numtheory): [seq(nops(cfrac(sqrt(2^k+1), 'periodic', 'quotients')[2]), k=4..28)];

CROSSREFS

Cf. A059866, A061682.

Adjacent sequences: A059923 A059924 A059925 this_sequence A059927 A059928 A059929

Sequence in context: A028941 A065045 A064947 this_sequence A138775 A121529 A006370

KEYWORD

nonn,nice

AUTHOR

Labos E. (labos(AT)ana.sote.hu), Mar 01 2001

EXTENSIONS

Two more terms from David W. Wilson (davidwwilson(AT)comcast.net), Jun 18 2001

Corrected and extended by Naohiro Nomoto (n_nomoto(AT)yabumi.com), Nov 09 2001

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Last modified November 8 20:39 EST 2009. Contains 166234 sequences.


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