%I A157998
%S A157998 168,674,1518,2700,4220,6078,8274,10808,13680,16890,20438,24324,28548,
%T A157998 33110,38010,43248,48824,54738,60990,67580,74508,81774,89378,97320,
%U A157998 105600,114218,123174,132468,142100,152070,162378,173024,184008,195330
%N A157998 a(n)=169*n^2-n (n>0)
%C A157998 If A=[A157998] 169*n.^2-n (168, 674, 1518,. ,.,); Y=[A010865] 26 (26, 
               26, 26,..,); X=[A157999] 338*n-1 (337, 675, 1013, ,. .,), we have, 
               for all terms, Pell's equation X^2-A*Y^2=1. Example: 337^2-168 *26^2=1; 
               675^2-674*26^2=1; 1013^2-1518*26^2=1.
%H A157998 Edward Everett Withford, <a href="http://quod.lib.umich.edu/cgi/t/text/
               text-idx?c=umhistmath;cc=umhistmath;idno=abv2773.0001.001;view=toc">
               Pell Equation</a>
%H A157998 Vincenzo Librandi, <a href="http://mathforum.org/kb/message.jspa?messageID=5785989&tstart=0">
               X^2-AY^2=1</a>
%H A157998 Wolfram MathWorld, <a href="http://mathworld.wolfram.com/PellEquation.html">
               Pell Equation</a>
%F A157998 a(n)=169*n^2-n (n>0)
%e A157998 For n=1, a(1)=168; n=2, a(2)=674; n=3, a(3)=1518
%Y A157998 Cf. A010865, A157999
%Y A157998 Sequence in context: A158219 A027679 A137863 this_sequence A110285 A070835 
               A112551
%Y A157998 Adjacent sequences: A157995 A157996 A157997 this_sequence A157999 A158000 
               A158001
%K A157998 nonn
%O A157998 1,1
%A A157998 Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Mar 11 2009