The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 6 |
| 6 | 32 |
| 7 | 199 |
| 8 | 1435 |
| 9 | 11741 |
| 10 | 107809 |
| 11 | 1097700 |
| 12 | 12274282 |
| 13 | 149523079 |
| 14 | 1970986052 |
| 15 | 27952165838 |
| 16 | 424364699554 |
| 17 | 6866992410974 |
| 18 | 117987415061286 |
| 19 | 2145225728387029 |
| 20 | 41149329880878477 |
| 21 | 830468293959547464 |
[1,0,0,0,1,6,32,199,1435,11741,107809,1097700, 12274282,149523079,1970986052,27952165838, 424364699554,6866992410974,117987415061286, 2145225728387029,41149329880878477, 830468293959547464] |