A225308 - cp's OEIS frontend

A225308 Number of n X 7 -1,1 arrays such that the sum over i=1..n, j=1..7 of i*x(i,j) is zero and rows are nondecreasing (ways to put 7 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	22
4	122
5	0
6	0
7	29638
8	197440
9	0
10	0
11	64811436
12	458450486
13	0
14	0
15	170747302728
16	1245085560292
17	0
18	0
19	497500354657954
20	3694982212755606
21	0
22	0
23	1544103180477715700
24	11609994393282630090
25	0
26	0
27	5004924971984927428464

[0, 0, 22, 122, 0, 0, 29638, 197440, 0, 0, 64811436, 458450486, 0, 0, 170747302728, 1245085560292, 0, 0, 497500354657954, 3694982212755606, 0, 0, 1544103180477715700, 11609994393282630090, 0, 0, 5004924971984927428464]

cp's OEIS Frontend

A225308 Number of n X 7 -1,1 arrays such that the sum over i=1..n, j=1..7 of i*x(i,j) is zero and rows are nondecreasing (ways to put 7 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