A360064 Number of 3-dimensional tilings of a 2 X 2 X n box using 1 X 1 X 1 cubes and trominos (L-shaped connection of 3 cubes).

1, 5, 89, 1177, 16873, 237977, 3366793, 47599097, 673035625, 9516252633, 134553882441, 1902506043833, 26900227288361, 380352114739609, 5377937177440009, 76040613721296249, 1075165950495479017, 15202163218500810073, 214948926180739194569

Offset: 0

Author

Gerhard Kirchner, Jan 30 2023

Keywords

• nonn
• easy

Comments

Recurrence 1 is derived in A359884, "3d-tilings of a 2 X 2 X n box" as a special case of a more general tiling problem: III, example 8.

Examples

			4 rotations:
   ___ ___     ___ ___
  |   |   |   |   |   | (cross sections)
  |   |___|   |___|___|
  |       |   |   |   |
  |_______|   |___|___| a(1) = 4 + 1 = 5.
		

Links

• Paolo Xausa, Table of n, a(n) for n = 0..850
• Index entries for linear recurrences with constant coefficients, signature (13,20,-64,112,224,-128).

Crossrefs

Cf. A006253, A001045, A033516, A335559, A359885, A359886, A360065, A360066.

Programs

Mathematica

LinearRecurrence[{13, 20, -64, 112, 224, -128}, {1, 5, 89, 1177, 16873, 237977}, 25] (* Paolo Xausa, Oct 02 2024 *)

Formula

G.f.: (1 - 8*x + 4*x^2 - 16*x^3) / (1 - 13*x - 20*x^2 + 64*x^3 - 112*x^4 - 224*x^5 + 128*x^6).

Recurrence 1:

a(n) = 5*a(n-1) + 2*b(n-1) + c(n-1) + d(n-1) + e(n-1) + 8*a(n-2) + 4*b(n-2) + c(n-2) + 2*d(n-2),

b(n) = 8*a(n-1) + 4*b(n-1) + 2*c(n-1),

c(n) = 20*a(n-1) + 6*b(n-1) + 4*c(n-1) + 4*d(n-1) + 2*e(n-1),

d(n) = 4*a(n-1), e(n) = 16*a(n-1) + 4*b(n-1),

with a(n), b(n), c(n), d(n), e(n) = 0 for n <= 0 except for a(0)=1.

Recurrence 2:

a(n) = 13*a(n-1) + 20*a(n-2) - 64*a(n-3) + 112*a(n-4) + 224*a(n-5) - 128*a(n-6) for n >= 6. For n < 6, recurrence 1 can be used.