OFFSET
0,4
LINKS
W. F. Klostermeyer, M. E. Mays, L. Soltes and G. Trapp, A Pascal rhombus, Fibonacci Quarterly, 35 (1997), 318-328.
Index entries for linear recurrences with constant coefficients, signature (4,-6,4,-1).
FORMULA
For n>1, a(n) = (1/6)*(n-2)*(n^2 + 8n - 21).
From R. J. Mathar, Feb 06 2010: (Start)
a(n) = 4*a(n-1) -6*a(n-2) +4*a(n-3) -a(n-4) for n >= 6.
G.f.: -x^3*(-2-x+2*x^2)/(x-1)^4. (End)
MATHEMATICA
Join[{0, 0}, LinearRecurrence[{4, -6, 4, -1}, {0, 2, 9, 22}, 45]] (* Georg Fischer, Dec 10 2019 *)
PROG
(PARI) a(n)=if(n>2, (n-2)*(n^2 + 8*n - 21)/6, 0) \\ Charles R Greathouse IV, Oct 18 2022
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, May 28 2005
STATUS
approved