A038018 Triangle: T(n,k), k<=n: groupoids with n elements and k idempotents.
1, 0, 1, 3, 4, 3, 978, 1485, 729, 138, 56630832, 75503872, 37755904, 8390656, 700688, 813802235250650, 1017252851596875
Offset: 0
Examples
Triangle begins:
1;
0, 1;
3, 4, 3;
978, 1485, 729, 138;
56630832, 75503872, 37755904, 8390656, 700688;
...