OFFSET
1,1
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
Index entries for linear recurrences with constant coefficients, signature (1,1,-1).
FORMULA
a(n) = 9*n - a(n-1) - 1, with n > 1, a(1)=4.
G.f.: x*(4 + 9*x - 4*x^2)/((1+x)*(x-1)^2). - Vincenzo Librandi, Sep 18 2013
a(n) = a(n-1) + a(n-2) - a(n-3). - Vincenzo Librandi, Sep 18 2013
E.g.f.: (1/4)*(9 - 16*exp(x) + (7 + 18*x)*exp(2*x))*exp(-x). - G. C. Greubel, Jul 21 2016
MATHEMATICA
Table[4 + 9 Floor[n/2], {n, 60}] (* Vincenzo Librandi, Sep 18 2013 *)
PROG
(Magma) [4+9*Floor(n/2): n in [1..60]]; // Bruno Berselli, Sep 18 2013
(PARI) a(n)=n\2*9 + 4 \\ Charles R Greathouse IV, Jul 21 2016
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Nov 25 2009
EXTENSIONS
New definition by Vincenzo Librandi Sep 18 2013
STATUS
approved