A225338 - cp's OEIS frontend

A225338 Number of n X 2 -1,1 arrays such that the sum over i=1..n, j=1..2 of i*x(i,j) is zero, the sum of x(i,j) is zero, and rows are nondecreasing (number of ways to distribute 2-across galley oarsmen left-right at n fore-aft positions so that there are no turning moments on the ship).

n	a(n)
0	1
1	1
2	1
3	1
4	3
5	7
6	15
7	33
8	77
9	181
10	443
11	1113
12	2837
13	7283
14	18909
15	49635
16	131427
17	350419
18	940417
19	2538857
20	6890577
21	18790165
22	51462893
23	141509487
24	390530601
25	1081369087
26	3003537529
27	8366306613
28	23366125605
29	65420219243
30	183585473369
31	516298786843
32	1454928750641

[1, 1, 1, 1, 3, 7, 15, 33, 77, 181, 443, 1113, 2837, 7283, 18909, 49635, 131427, 350419, 940417, 2538857, 6890577, 18790165, 51462893, 141509487, 390530601, 1081369087, 3003537529, 8366306613, 23366125605, 65420219243, 183585473369, 516298786843, 1454928750641]

cp's OEIS Frontend

A225338 Number of n X 2 -1,1 arrays such that the sum over i=1..n, j=1..2 of i*x(i,j) is zero, the sum of x(i,j) is zero, and rows are nondecreasing (number of ways to distribute 2-across galley oarsmen left-right at n fore-aft positions so that there are no turning moments on the ship).

Table of values

List of values