Number of nX4 -1,1 arrays such that the sum over i=1..n,j=1..4 of i*x(i,j) is zero, the sum of x(i,j) is zero, and rows are nondecreasing (number of ways to distribute 4-across galley oarsmen left-right at n fore-aft positions so that there are no turning moments on the ship).
A225340
Number of nX4 -1,1 arrays such that the sum over i=1..n,j=1..4 of i*x(i,j) is zero, the sum of x(i,j) is zero, and rows are nondecreasing (number of ways to distribute 4-across galley oarsmen left-right at n fore-aft positions so that there are no turning moments on the ship).
Terms
- a(0) =1a(1) =1a(2) =3a(3) =9a(4) =31a(5) =107a(6) =395a(7) =1525a(8) =6095a(9) =24893a(10) =103583a(11) =437763a(12) =1874497a(13) =8116459a(14) =35485099a(15) =156453779a(16) =694956997a(17) =3107415563a(18) =13976787615a(19) =63201012187a(20) =287163163723
External references
- oeis: A225340