OFFSET
1,1
COMMENTS
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).
G.f.: x*(531 + 198*x)/(1-x)^2.
E.g.f.: 9*(22 - (22 - 81*x)*exp(x)). - G. C. Greubel, Jun 19 2021
MATHEMATICA
LinearRecurrence[{2, -1}, {531, 1260}, 40]
PROG
(Magma) I:=[531, 1260]; [n le 2 select I[n] else 2*Self(n-1)-Self(n-2): n in [1..50]];
(PARI) a(n)=729*n-198 \\ Charles R Greathouse IV, Dec 23 2011
(Sage) [9*(81*n -22) for n in [1..50]] # G. C. Greubel, Jun 19 2021
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Feb 15 2009
STATUS
approved