A225347 Number of 7Xn -1,1 arrays such that the sum over i=1..7,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 7 fore-aft positions so that there are no turning moments on the ship).
0, 33, 0, 395, 0, 2073, 0, 7261, 0, 19709, 0, 45385, 0, 92673, 0, 173189, 0, 301799, 0, 497661, 0, 783969, 0, 1189311, 0, 1747059, 0, 2497109, 0, 3484867, 0, 4763439, 0, 6392095, 0, 8439027, 0, 10979255, 0, 14097919, 0, 17887629, 0, 22452391, 0
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
Links
- R. H. Hardin, Table of n, a(n) for n = 1..210
Formula
Empirical: a(n) = a(n-2) +a(n-4) -a(n-10) -2*a(n-14) +a(n-18) +a(n-20) +a(n-22) +a(n-24) -2*a(n-28) -a(n-32) +a(n-38) +a(n-40) -a(n-42)
Comments