Triangle read by rows: T(n,k) = 2 - (1 + k)^k + (1 + n)^n - (1 - k + n)^(n - k).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =7a(5) =1a(6) =1a(7) =55a(8) =55a(9) =1a(10) =1a(11) =561a(12) =609a(13) =561a(14) =1a(15) =1a(16) =7151a(17) =7705a(18) =7705a(19) =7151a(20) =1a(21) =1a(22) =109873a(23) =117017a(24) =117523a(25) =117017a(26) =109873a(27) =1a(28) =1a(29) =1979503