T(n,k)=Number of nXk zero-sum -1..1 arrays with rows and columns lexicographically nondecreasing.

Terms

a(0) =1a(1) =2a(2) =2a(3) =2a(4) =7a(5) =2a(6) =3a(7) =21a(8) =21a(9) =3a(10) =3a(11) =56a(12) =181a(13) =56a(14) =3a(15) =4a(16) =130a(17) =1341a(18) =1341a(19) =130a(20) =4a(21) =4a(22) =281a(23) =8312a(24) =29363a(25) =8312a(26) =281a(27) =4a(28) =5a(29) =555