OFFSET
1,3
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..10000
Index entries for linear recurrences with constant coefficients, signature (-4,-6,-4,-1).
FORMULA
a(n) = -4*a(n-1) - 6*a(n-2) - 4*a(n-3) - a(n-4).
G.f.: x*(1+3*x)/(1+x)^4.
MATHEMATICA
Table[n (-1)^n*(n + 1) (2*n - 5)/6, {n, 60}] (* Vladimir Joseph Stephan Orlovsky, Jul 08 2011 *)
PROG
(PARI) a(n)=(-1)^n*n*(n+1)*(2*n-5)/6 \\ Charles R Greathouse IV, Aug 24 2011
(Magma) [(-1)^n*n*(n+1)*(2*n-5)/6: n in [1..50]]; // Vincenzo Librandi, Aug 25 2011
CROSSREFS
KEYWORD
sign,easy
AUTHOR
Jamel Ghanouchi, Nov 02 2009
EXTENSIONS
Note that for a sequence in which every other term is zero, the OEIS policy is to omit those zeros. - N. J. A. Sloane, Nov 08 2009
Zeros removed by skipping even-indexed polynomials - R. J. Mathar, Nov 12 2009
STATUS
approved