A054121 T(n,n-3), array T as in A054120.

1, 9, 39, 114, 261, 507, 879, 1404, 2109, 3021, 4167, 5574, 7269, 9279, 11631, 14352, 17469, 21009, 24999, 29466, 34437, 39939, 45999, 52644, 59901, 67797, 76359, 85614, 95589, 106311, 117807, 130104, 143229, 157209

Offset: 3

Author

Clark Kimberling

Keywords

• nonn
• easy

Links

• Index entries for linear recurrences with constant coefficients, signature (4,-6,4,-1)

Programs

Mathematica

LinearRecurrence[{4,-6,4,-1},{1,9,39,114,261},40] (* Harvey P. Dale, Sep 28 2017 *)

PARI

a(n)=max(9*n^3-90*n^2+321*n-402,2)/2  \\ Charles R Greathouse IV, Oct 19 2022

Formula

For n>3, a(n) = 3/2 * (3n^3-30n^2+107n-134).