The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 1 |
| 4 | 5 |
| 5 | 12 |
| 6 | 58 |
| 7 | 220 |
| 8 | 1145 |
| 9 | 5684 |
| 10 | 33284 |
| 11 | 198412 |
| 12 | 1306355 |
| 13 | 8945046 |
| 14 | 65658392 |
| 15 | 503505600 |
| 16 | 4076565489 |
| 17 | 34442610648 |
| 18 | 304577372128 |
| 19 | 2802673411280 |
| 20 | 26840614943667 |
| 21 | 266644080930194 |
| 22 | 2745669007978680 |
| 23 | 29243006731749200 |
| 24 | 321810005123384617 |
| 25 | 3653558357684804324 |
[1,0,1,1,5,12,58,220,1145,5684,33284,198412, 1306355,8945046,65658392,503505600,4076565489, 34442610648,304577372128,2802673411280, 26840614943667,266644080930194,2745669007978680, 29243006731749200,321810005123384617, 3653558357684804324] |