A257666 Number of ways of placing n balls into boxes 1,2,... in such a way that any two adjacent boxes contain at least 4 balls.

1, 1, 1, 1, 7, 11, 17, 25, 51, 94, 165, 280, 496, 887, 1576, 2770, 4880, 8630, 15276, 26990, 47656, 84183, 148781, 262921, 464528, 820699, 1450091, 2562250, 4527272, 7999104, 14133456, 24972396, 44123768, 77962003, 137750326, 243390090, 430044755, 759843749

Offset: 0

Author

Alois P. Heinz, Jul 12 2015

Keywords

• nonn
• easy

Links

• Alois P. Heinz, Table of n, a(n) for n = 0..1000
• Index entries for linear recurrences with constant coefficients, signature (0,1,1,3,3,1,0,-1,-1).

Crossrefs

Rows sums of A259975.

Programs

Mathematica

LinearRecurrence[{0,1,1,3,3,1,0,-1,-1},{1,1,1,1,7,11,17,25,51,94},40] (* Harvey P. Dale, Jul 12 2019 *)

Formula

G.f.: -(x^9+x^8-2*x^6-3*x^5-2*x^4+x^3-x-1) / ((1+x) *(x^8 -x^5 -2*x^4 -x^3 -x+1)).