OFFSET
1,1
COMMENTS
The identity (1250*n^2 - 100*n + 1)^2 - (25*n^2 - 2*n)*(250*n - 10)^2 = 1 can be written as A154374(n)^2 - A154376(n)*a(n)^2 = 1 (see also the second comment in A154374). - Vincenzo Librandi, Jan 30 2012
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..10000
Index entries for linear recurrences with constant coefficients, signature (2,-1).
FORMULA
a(n) = 2*a(n-1) - a(n-2). - Vincenzo Librandi, Jan 30 2012
G.f.: 10*x*(x + 24)/(1-x)^2. - Vincenzo Librandi, Jan 30 2012
E.g.f.: 10*( (25*x - 1)*exp(x) + 1). - G. C. Greubel, Sep 15 2016
MATHEMATICA
LinearRecurrence[{2, -1}, {240, 490}, 50] (* Vincenzo Librandi, Jan 30 2012 *)
PROG
(PARI) a(n)=250*n-10 \\ Charles R Greathouse IV, Dec 27 2011
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Jan 08 2009
STATUS
approved