| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 23 |
| 5 | 103 |
| 6 | 515 |
| 7 | 2803 |
| 8 | 16334 |
| 9 | 100700 |
| 10 | 650905 |
| 11 | 4380595 |
| 12 | 30528410 |
| 13 | 219352058 |
| 14 | 1619260140 |
| 15 | 12245357074 |
| 16 | 94636062782 |
| 17 | 745907086918 |
| 18 | 5985448211508 |
| 19 | 48824435255942 |
| 20 | 404330087326924 |
| 21 | 3395418226577756 |
| 22 | 28884708430087203 |
| 23 | 248696210256230427 |
[1,1,2,6,23,103,515,2803,16334,100700,650905, 4380595,30528410,219352058,1619260140,12245357074, 94636062782,745907086918,5985448211508, 48824435255942,404330087326924,3395418226577756, 28884708430087203,248696210256230427] |