

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
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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



