A225304 - cp's OEIS frontend

A225304 Number of nX3 -1,1 arrays such that the sum over i=1..n,j=1..3 of i*x(i,j) is zero and rows are nondecreasing (ways to put 3 thrusters pointing east or west at each of n positions 1..n distance from the hinge of a south-pointing gate without turning the gate).

n	a(n)
1	0
2	0
3	6
4	16
5	0
6	0
7	474
8	1576
9	0
10	0
11	64700
12	228876
13	0
14	0
15	10659862
16	38869960
17	0
18	0
19	1941920508
20	7211917300
21	0
22	0
23	376790653888
24	1416598649968
25	0
26	0
27	76344225166632
28	289560610889154
29	0
30	0
31	15965033749025502
32	60953934482465398
33	0
34	0

[0, 0, 6, 16, 0, 0, 474, 1576, 0, 0, 64700, 228876, 0, 0, 10659862, 38869960, 0, 0, 1941920508, 7211917300, 0, 0, 376790653888, 1416598649968, 0, 0, 76344225166632, 289560610889154, 0, 0, 15965033749025502, 60953934482465398, 0, 0]

cp's OEIS Frontend

A225304 Number of nX3 -1,1 arrays such that the sum over i=1..n,j=1..3 of i*x(i,j) is zero and rows are nondecreasing (ways to put 3 thrusters pointing east or west at each of n positions 1..n distance from the hinge of a south-pointing gate without turning the gate).

Table of values

List of values