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

Author

Andrew Howroyd, Dec 11 2024

Keywords

• nonn
• easy

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).

Crossrefs

Row 3 of A378932.

Cf. A166761, A359988, A378934.

Programs

Mathematica

LinearRecurrence[{6, -14, 16, -9, 2}, {2, 15, 53, 146, 356}, 30] (* Paolo Xausa, Mar 02 2025 *)

PARI

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

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.