| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 2 |
| 4 | 15 |
| 5 | 44 |
| 6 | 475 |
| 7 | 2274 |
| 8 | 33313 |
| 9 | 227240 |
| 10 | 2920041 |
| 11 | 26754650 |
| 12 | 469513231 |
| 13 | 4613913732 |
| 14 | 85842524755 |
| 15 | 1174844041994 |
| 16 | 24672317426625 |
| 17 | 334246510927184 |
| 18 | 7985602649948113 |
| 19 | 127351500133158450 |
| 20 | 3282809137540001551 |
| 21 | 60776696924693716700 |
| 22 | 1556379682561575238731 |
| 23 | 32568139442090869594802 |
[1,0,1,2,15,44,475,2274,33313,227240,2920041, 26754650,469513231,4613913732,85842524755, 1174844041994,24672317426625,334246510927184, 7985602649948113,127351500133158450, 3282809137540001551,60776696924693716700, 1556379682561575238731,32568139442090869594802] |