A225305 - cp's OEIS frontend

A225305 Number of nX4 -1,1 arrays such that the sum over i=1..n,j=1..4 of i*x(i,j) is zero and rows are nondecreasing (ways to put 4 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	1
2	3
3	9
4	31
5	113
6	443
7	1787
8	7445
9	31593
10	136351
11	596187
12	2636015
13	11763569
14	52920569
15	239731317
16	1092632909
17	5006816043
18	23053197067
19	106601983853
20	494856940025
21	2305237337415
22	10772988573393
23	50491926308985

[1, 3, 9, 31, 113, 443, 1787, 7445, 31593, 136351, 596187, 2636015, 11763569, 52920569, 239731317, 1092632909, 5006816043, 23053197067, 106601983853, 494856940025, 2305237337415, 10772988573393, 50491926308985]

cp's OEIS Frontend

A225305 Number of nX4 -1,1 arrays such that the sum over i=1..n,j=1..4 of i*x(i,j) is zero and rows are nondecreasing (ways to put 4 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