cp's OEIS Frontend

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).

%I A225340 #6 Jun 02 2025 08:32:50
%S A225340 1,1,3,9,31,107,395,1525,6095,24893,103583,437763,1874497,8116459,
%T A225340 35485099,156453779,694956997,3107415563,13976787615,63201012187,
%U A225340 287163163723,1310481411725,6004334305049,27611237977705,127399143883589
%N 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).
%C A225340 Column 4 of A225345
%H A225340 R. H. Hardin, <a href="/A225340/b225340.txt">Table of n, a(n) for n = 1..135</a>
%e A225340 Some solutions for n=4
%e A225340 .-1..1..1..1....1..1..1..1...-1.-1.-1.-1...-1.-1..1..1...-1..1..1..1
%e A225340 .-1.-1.-1.-1...-1.-1.-1.-1....1..1..1..1...-1.-1..1..1...-1.-1.-1..1
%e A225340 .-1..1..1..1...-1.-1.-1.-1....1..1..1..1...-1.-1..1..1...-1.-1.-1..1
%e A225340 .-1.-1..1..1....1..1..1..1...-1.-1.-1.-1...-1.-1..1..1...-1..1..1..1
%K A225340 nonn
%O A225340 1,3
%A A225340 _R. H. Hardin_ May 05 2013