OFFSET
1,1
COMMENTS
The identity (900*n + 1)^2 - (900*n^2 + 2*n)*30^2 = 1 can be written as a(n)^2 - A158406(n)*(30)^2 = 1. - Vincenzo Librandi, Feb 09 2012
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..10000
Vincenzo Librandi, X^2-AY^2=1
Index entries for linear recurrences with constant coefficients, signature (2,-1).
FORMULA
G.f.: x*(901-x)/(1-x)^2. - Vincenzo Librandi, Feb 09 2012
a(n) = 2*a(n-1) - a(n-2). - Vincenzo Librandi, Feb 09 2012
MATHEMATICA
LinearRecurrence[{2, -1}, {901, 1801}, 50] (* Vincenzo Librandi, Feb 09 2012 *)
900*Range[40]+1 (* Harvey P. Dale, Aug 18 2019 *)
PROG
(Magma) I:=[901, 1801]; [n le 2 select I[n] else 2*Self(n-1)-Self(n-2): n in [1..50]]; // Vincenzo Librandi, Feb 09 2012
(PARI) for(n=1, 40, print1(900*n + 1", ")); \\ Vincenzo Librandi, Feb 09 2012
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Mar 18 2009
STATUS
approved