%I A157510
%S A157510 1020,2020,3020,4020,5020,6020,7020,8020,9020,10020,11020,12020,13020,
%T A157510 14020,15020,16020,17020,18020,19020,20020,21020,22020,23020,24020,
%U A157510 25020,26020,27020,28020,29020,30020,31020,32020,33020,34020,35020
%N A157510 a(n)=1000*n+20 (n>0)
%C A157510 If A=[A031434] 25*n.^2+n (26,102,228,.,); Y=[A157510] 1000*n+20 (1020,
               2020,3020..,); X=[A157511] 5000*n^2+200*n+1 (5201,20401,45601,.,), 
               we have, for all terms, Pell's equation X^2-A*Y^2=1. Example: 5201^2-26*1020^2=1; 
               20401^2-102*2020^2=1; 45601^2-228*3020^2=1.
%H A157510 Wolfram MathWorld, <a href="http://mathworld.wolfram.com/PellEquation.html">
               Pell Equation</a>
%H A157510 Vincenzo Librandi, <a href="http://mathforum.org/kb/message.jspa?messageID=5771301&tstart=0">
               X^2-AY^2=1</a>
%F A157510 a(n)=1000*n+20 (n>0)
%e A157510 For n=1, a(1)=1020; n=2, a(2)=2020; n=3, a(3)=3020
%Y A157510 Cf. A031434, A157511
%Y A157510 Sequence in context: A087837 A051982 A104444 this_sequence A015160 A102925 
               A024020
%Y A157510 Adjacent sequences: A157507 A157508 A157509 this_sequence A157511 A157512 
               A157513
%K A157510 nonn
%O A157510 1,1
%A A157510 Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Mar 02 2009