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).
1, 1, 3, 9, 31, 107, 395, 1525, 6095, 24893, 103583, 437763, 1874497, 8116459, 35485099, 156453779, 694956997, 3107415563, 13976787615, 63201012187, 287163163723, 1310481411725, 6004334305049, 27611237977705, 127399143883589
Offset: 1
Keywords
Examples
Some solutions for n=4 .-1..1..1..1....1..1..1..1...-1.-1.-1.-1...-1.-1..1..1...-1..1..1..1 .-1.-1.-1.-1...-1.-1.-1.-1....1..1..1..1...-1.-1..1..1...-1.-1.-1..1 .-1..1..1..1...-1.-1.-1.-1....1..1..1..1...-1.-1..1..1...-1.-1.-1..1 .-1.-1..1..1....1..1..1..1...-1.-1.-1.-1...-1.-1..1..1...-1..1..1..1
Links
- R. H. Hardin, Table of n, a(n) for n = 1..135
Comments