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%I #17 Jun 17 2017 03:04:48
%S 323,647,971,1295,1619,1943,2267,2591,2915,3239,3563,3887,4211,4535,
%T 4859,5183,5507,5831,6155,6479,6803,7127,7451,7775,8099,8423,8747,
%U 9071,9395,9719,10043,10367,10691,11015,11339,11663,11987,12311,12635,12959
%N 324n - 1.
%C The identity (324*n-1)^2-(324*n^2-2*n)*(18)^2=1 can be written as a(n)^2-A158305(n)*(18)^2=1.
%H Vincenzo Librandi, <a href="/A158306/b158306.txt">Table of n, a(n) for n = 1..10000</a>
%H Vincenzo Librandi, <a href="http://mathforum.org/kb/message.jspa?messageID=5785989&tstart=0">X^2-AY^2=1</a>
%H E. J. Barbeau, <a href="http://www.math.toronto.edu/barbeau/home.html">Polynomial Excursions</a>, Chapter 10: <a href="http://www.math.toronto.edu/barbeau/hxpol10.pdf">Diophantine equations</a> (2010), pages 84-85 (row 15 in the first table at p. 85, case d(t) = t*(18^2*t-2)).
%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1).
%F a(n) = 2*a(n-1)-a(n-2).
%F G.f.: x*(323+x)/(1-x)^2.
%t 324Range[50]-1 (* _Harvey P. Dale_, Mar 13 2011 *)
%Y Cf. A158305.
%K nonn,easy
%O 1,1
%A _Vincenzo Librandi_, Mar 16 2009
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