%I A158591
%S A158591 1,37,145,325,577,901,1297,1765,2305,2917,3601,4357,5185,6085,7057,8101,
%T A158591 9217,10405,11665,12997,14401,15877,17425,19045,20737,22501,24337,26245,
%U A158591 28225,30277,32401,34597,36865,39205,41617,44101,46657,49285,51985
%N A158591 a(n)=36*n^2+1.
%C A158591 The identity (36*n^2+1)^2 - (324*n^2+18)*(2*n)^2 = 1 can be written in
%C A158591 Pell-format as (a(n))^2 - A158590(n)* (A005843(n))^2 =1.
%H A158591 Vincenzo Librandi, <a href="http://mathforum.org/kb/message.jspa?messageID=5785989&tstart=0">
               X^2-AY^2=1</a>
%H A158591 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 A158591 Wolfram MathWorld, <a href="http://mathworld.wolfram.com/PellEquation.html">
               Pell Equation</a>
%F A158591 a(n)= 3*a(n-1) -3*a(n-2) +a(n-3). G.f: -(1+34*x+37*x^2)/(x-1)^3.
%Y A158591 Cf. A005843, A158590
%Y A158591 Sequence in context: A044750 A141936 A142498 this_sequence A031690 A157324 
               A141968
%Y A158591 Adjacent sequences: A158588 A158589 A158590 this_sequence A158592 A158593 
               A158594
%K A158591 nonn,easy
%O A158591 0,2
%A A158591 Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Mar 22 2009
%E A158591 Comment rewritten, formula replaced by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), 
               Oct 28 2009