A027116 a(n) = A027113(n, n+3).

7, 23, 56, 120, 241, 467, 886, 1660, 3087, 5715, 10552, 19452, 35825, 65943, 121342, 223240, 410663, 755391, 1389448, 2555664, 4700673, 8645963, 15902486, 29249316, 53797967, 98949979, 181997480, 334745652, 615693345

Offset: 3

Author

Clark Kimberling

Keywords

• nonn

Formula

Conjectures from Colin Barker, Feb 20 2016: (Start)

a(n) = 3*a(n-1)-2*a(n-2)-a(n-4)+a(n-5) for n>7.

G.f.: x^3*(7+2*x+x^2-2*x^3) / ((1-x)^2*(1-x-x^2-x^3)).

(End)