%I
%S 9803,9811,9839,9843,9851,9859,9871,9883,9887,9899,9907,9923,9931,
%T 9959,9963,9967,9987,9991,10007,10019,10031,10039,10067,10079,10083,
%U 10091,10099,10103,10107,10111,10131,10139,10147,10151,10159,10163,10199,39208
%N Numbers n such that continued fraction for sqrt(n) has even period and central term 99.
%H Chai Wah Wu, <a href="/A031597/b031597.txt">Table of n, a(n) for n = 1..10000</a>
%o (Python)
%o from __future__ import division
%o from sympy import continued_fraction_periodic
%o A031597_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) % 2 == 0 and s[len(s)//21] == 99] # _Chai Wah Wu_, Jun 10 2017
%K nonn
%O 1,1
%A _David W. Wilson_
