A123777 - cp's OEIS frontend

A123777 Number of ways to build a contiguous building with n LEGO blocks of size 1 X 3 on top of a fixed block of the same size so that the building is flat, i.e., with all blocks in parallel position and symmetric after a rotation by 180 degrees.

n	a(n)
1	1
2	2
3	3
4	7
5	14
6	37
7	76
8	217
9	473
10	1374
11	3104
12	9196
13	21240
14	63929
15	150294
16	456703
17	1089683
18	3338624
19	8055267
20	24845592
21	60511113
22	187665038
23	460638240

[1, 2, 3, 7, 14, 37, 76, 217, 473, 1374, 3104, 9196, 21240, 63929, 150294, 456703, 1089683, 3338624, 8055267, 24845592, 60511113, 187665038, 460638240]

cp's OEIS Frontend

A123777 Number of ways to build a contiguous building with n LEGO blocks of size 1 X 3 on top of a fixed block of the same size so that the building is flat, i.e., with all blocks in parallel position and symmetric after a rotation by 180 degrees.

Table of values

List of values