A(2,2) = 4: (1,1), (1,2), (1,3), (1,4).
A(2,3) = 8: (1,1), (1,2), (1,3), (1,4), (1,5), (1,6), (1,7), (1,8).
A(3,1) = 5: (1,1,1), (1,1,2), (1,1,3), (1,2,2), (1,2,3).
Square array A(n,k) begins:
1, 1, 1, 1, 1, 1, ...
1, 1, 1, 1, 1, 1, ...
1, 2, 4, 8, 16, 32, ...
1, 5, 30, 188, 1176, 7280, ...
1, 14, 340, 9280, 249776, 6518784, ...
1, 42, 5235, 804322, 119088660, 16633660072, ...