a(n,m) tabl head (triangle) for A064879 n\m 0 1 2 3 4 5 6 7 8 9 ... 0 1 0 0 0 0 0 0 0 0 0 1 1 1 0 0 0 0 0 0 0 0 2 0 1 1 0 0 0 0 0 0 0 3 0 2 1 1 0 0 0 0 0 0 4 0 5 4 1 1 0 0 0 0 0 5 0 14 28 6 1 1 0 0 0 0 6 0 42 256 81 8 1 1 0 0 0 7 0 132 2704 1566 176 10 1 1 0 0 8 0 429 31168 36126 5888 325 12 1 1 0 9 0 1430 380608 921456 238848 16750 540 14 1 1 . . . Row sums give A064880: [1,2,2,4,11,50,389,4590,73950,1559648,...] ################################################ e.o.f. ######################################