login

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

Number of 5X2 integer matrices with each row summing to zero, row elements in nondecreasing order, rows in lexicographically nondecreasing order, and the sum of squares of the elements <= 2*n^2 (number of collections of 5 zero-sum 2-vectors with total modulus squared not more than 2*n^2, ignoring vector and component permutations)
1

%I #5 Mar 31 2012 12:36:20

%S 2,6,14,29,56,101,166,267,407,604,865,1211,1659,2236,2956,3861,4949,

%T 6299,7906,9849,12120,14817,17958,21641,25859,30753,36318,42732,49917,

%U 58116,67296,77693,89219,102175,116527,132515,150117,169602,191013,214662

%N Number of 5X2 integer matrices with each row summing to zero, row elements in nondecreasing order, rows in lexicographically nondecreasing order, and the sum of squares of the elements <= 2*n^2 (number of collections of 5 zero-sum 2-vectors with total modulus squared not more than 2*n^2, ignoring vector and component permutations)

%C Column (5,2,n) of A192710

%H R. H. Hardin, <a href="/A192705/b192705.txt">Table of n, a(n) for n = 1..200</a>

%e Some solutions for 5X2 <= 2*4^2

%e .-3..3...-2..2...-2..2...-1..1...-1..1...-2..2...-3..3...-3..3...-3..3...-2..2

%e .-1..1...-1..1...-2..2...-1..1...-1..1...-2..2...-1..1....0..0...-1..1...-2..2

%e .-1..1...-1..1...-1..1....0..0...-1..1...-2..2...-1..1....0..0....0..0...-2..2

%e .-1..1....0..0...-1..1....0..0....0..0...-2..2...-1..1....0..0....0..0....0..0

%e .-1..1....0..0...-1..1....0..0....0..0....0..0....0..0....0..0....0..0....0..0

%K nonn

%O 1,1

%A _R. H. Hardin_ Jul 07 2011