The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 2 |
| 3 | 15 |
| 4 | 92 |
| 5 | 930 |
| 6 | 8514 |
| 7 | 116760 |
| 8 | 1445744 |
| 9 | 23020200 |
| 10 | 373858920 |
| 11 | 6756785640 |
| 12 | 130982295432 |
| 13 | 2751191997840 |
| 14 | 61046788571664 |
| 15 | 1445520760702200 |
| 16 | 36387213668348160 |
| 17 | 960383111961228480 |
| 18 | 26780931923301572544 |
| 19 | 781864626481646405760 |
| 20 | 23925584882896903854720 |
[1,0,2,15,92,930,8514,116760,1445744,23020200, 373858920,6756785640,130982295432,2751191997840, 61046788571664,1445520760702200,36387213668348160, 960383111961228480,26780931923301572544, 781864626481646405760,23925584882896903854720] |