A225348 Number of 8Xn -1,1 arrays such that the sum over i=1..8,j=1..n of i*x(i,j) is zero, the sum of x(i,j) is zero, and rows are nondecreasing (number of ways to distribute n-across galley oarsmen left-right at 8 fore-aft positions so that there are no turning moments on the ship).
8, 77, 410, 1525, 4508, 11291, 25056, 50659, 95130, 168289, 283338, 457627, 713374, 1078615, 1587974, 2283803, 3217102, 4448769, 6050622, 8106883, 10715232, 13988475, 18055740, 23064277, 29180742, 36593245, 45512628, 56174753, 68841880
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 .-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..210
Formula
Empirical: a(n) = a(n-1) +a(n-2) -a(n-5) -a(n-7) -a(n-8) +a(n-10) +a(n-11) +2*a(n-12) -2*a(n-16) -a(n-17) -a(n-18) +a(n-20) +a(n-21) +a(n-23) -a(n-26) -a(n-27) +a(n-28)
Comments