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A031597 Numbers n such that continued fraction for sqrt(n) has even period and central term 99. 1

%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)//2-1] == 99] # _Chai Wah Wu_, Jun 10 2017

%K nonn

%O 1,1

%A _David W. Wilson_

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Last modified February 28 09:52 EST 2020. Contains 332323 sequences. (Running on oeis4.)