A192712 - OEIS

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

%S 2,6,19,51,126,285,604,1208,2310,4237,7513,12885,21536,35072,55893,

%T 87271,133793,201572,299171,437546,631447,900231,1268643,1768448,

%U 2440754,3336495,4520239,6073339,8095214,10708816,14066591,18351402,23788458

%N Number of 11X2 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 11 zero-sum 2-vectors with total modulus squared not more than 2*n^2, ignoring vector and component permutations)

%C Column (11,2,n) of A192710

%H R. H. Hardin, <a href="/A192712/b192712.txt">Table of n, a(n) for n = 1..75</a>

%e Some solutions for 11X2 <= 2*4^2

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

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

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

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

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

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

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

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

%e ..0..0....0..0....0..0....0..0....0..0....0..0....0..0....0..0....0..0....0..0

%e ..0..0....0..0....0..0....0..0....0..0....0..0....0..0....0..0....0..0....0..0

%e ..0..0....0..0....0..0....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