A378933 Number of minimal edge cuts in the 3 X n grid graph.

2, 15, 53, 146, 356, 809, 1759, 3716, 7702, 15763, 31993, 64582, 129912, 260749, 522627, 1046616, 2094858, 4191639, 8385533, 16773690, 33550412, 67104305, 134212583, 268429676, 536864446, 1073734619, 2147475649, 4294958446, 8589924832, 17179858453

Offset

1,1

Links

Andrew Howroyd, Table of n, a(n) for n = 1..200

Index entries for linear recurrences with constant coefficients, signature (6,-14,16,-9,2).

Formula

a(n) = 16*2^n - (2*n^3 + 9*n^2 + 73*n + 96)/6.

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

a(n) = A166761(n)/2.

Prog

(PARI) a(n) = {16*2^n - (2*n^3 + 9*n^2 + 73*n + 96)/6}

Crossrefs

Row 3 of A378932.

Cf. A166761, A359988, A378934.

Sequence in context: A015520 A098520 A216333 * A056078 A142861 A305673

Adjacent sequences: A378923 A378924 A378932 * A378934 A378935 A378936

Keyword

nonn,easy,new

Author

Andrew Howroyd, Dec 11 2024

Status

approved