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%I #15 Jul 11 2021 07:23:18
%S 1621,3001,3637,4153,5113,5653,7114,8026,9161,12538,12569,13261,14177,
%T 18058,19373,21625,25733,25981,26297,28277,28394,29674,30122,32201,
%U 32393,32861,33773,34801,35746,36137,36185,36257,36994,39049,39701,41429,43721
%N Numbers k such that the continued fraction for sqrt(k) has period 79.
%H Chai Wah Wu, <a href="/A020418/b020418.txt">Table of n, a(n) for n = 1..10000</a>
%t cf79Q[n_]:=Module[{c=Sqrt[n]},!IntegerQ[c]&&Length[ContinuedFraction[c][[2]]]==79]; Select[Range[50000],cf79Q] (* _Harvey P. Dale_, Dec 23 2012 *)
%o (Python)
%o from sympy import continued_fraction_periodic
%o A020418_list = [n for n, s in ((i, continued_fraction_periodic(0,1,i)[-1]) for i in range(1,10**5)) if isinstance(s, list) and len(s) == 79] # _Chai Wah Wu_, Jun 08 2017
%K nonn
%O 1,1
%A _David W. Wilson_
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