Square array read by antidiagonals: T(m,n) = number of spanning trees in an m X n grid.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =4a(5) =1a(6) =1a(7) =15a(8) =15a(9) =1a(10) =1a(11) =56a(12) =192a(13) =56a(14) =1a(15) =1a(16) =209a(17) =2415a(18) =2415a(19) =209a(20) =1a(21) =1a(22) =780a(23) =30305a(24) =100352a(25) =30305a(26) =780a(27) =1a(28) =1a(29) =2911