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A010338 Numbers k such that the continued fraction for sqrt(k) has period 7. 2
58, 73, 202, 250, 274, 314, 349, 425, 538, 761, 1010, 1073, 1130, 1301, 1546, 1745, 1825, 1898, 2050, 2173, 2258, 2330, 2482, 2581, 2777, 3161, 3202, 3554, 3877, 3890, 4106, 4133, 4346, 4586, 4925, 5162, 5261, 5273, 5297, 5305 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Chai Wah Wu, Table of n, a(n) for n = 1..10000 (terms n = 1..500 from Harvey P. Dale)

MATHEMATICA

cfp7Q[n_]:=Module[{s=Sqrt[n]}, !IntegerQ[s]&&Length[ ContinuedFraction[ s][[2]]]==7]; Select[Range[6000], cfp7Q] (* Harvey P. Dale, Aug 11 2013 *)

PROG

(Python)

from sympy import continued_fraction_periodic

A010338_list = [n for n, s in ((i, continued_fraction_periodic(0, 1, i)[-1]) for i in range(1, 10**3)) if isinstance(s, list) and len(s) == 7] # Chai Wah Wu, Jun 08 2017

CROSSREFS

Sequence in context: A224359 A226036 A127024 * A184074 A281824 A127334

Adjacent sequences:  A010335 A010336 A010337 * A010339 A010340 A010341

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Walter Gilbert

STATUS

approved

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Last modified December 9 03:23 EST 2021. Contains 349625 sequences. (Running on oeis4.)