A124976 Table (read by antidiagonals): t(1,n) = t(m,1) = 1 for all m and n. t(m,n) = (sum{k=1 to m-1} t(k,n)) * (sum{k=1 to n-1} t(m,k)).

1, 1, 1, 1, 1, 1, 1, 2, 2, 1, 1, 4, 9, 4, 1, 1, 8, 60, 60, 8, 1, 1, 16, 648, 4225, 648, 16, 1, 1, 32, 12240, 2818530, 2818530, 12240, 32, 1, 1, 64, 427680, 34599304740, 7947815340969, 34599304740, 427680, 64, 1, 1, 128, 28641600, 14799779785070280

Offset

1,8

Links

Table of n, a(n) for n=1..49.

Example

t(3,4) = (t(1,4)+t(2,4)) * (t(3,1)+t(3,2)+t(3,3)) = (1+4) * (1+2+9) = 60.

Mathematica

t[m_, n_] := t[m, n] = If[m == 1 || n == 1, 1, Sum[t[k, n], {k, m - 1}] * Sum[t[m, j], {j, n - 1}]]; Flatten@Table[t[d + 1 - j, j], {d, 10}, {j, d}] (* Ray Chandler, Nov 19 2006 *)

Crossrefs

Cf. A124975.

Sequence in context: A342623 A121697 A225201 * A176663 A113021 A298261

Adjacent sequences: A124973 A124974 A124975 * A124977 A124978 A124979

Keyword

easy,nonn,tabl

Author

Leroy Quet, Nov 14 2006

Extensions

Extended by Ray Chandler, Nov 19 2006

Status

approved