| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 20 |
| 3 | 270 |
| 4 | 3000 |
| 5 | 23282 |
| 6 | 151473 |
| 7 | 768541 |
| 8 | 3422978 |
| 9 | 12879078 |
| 10 | 44111410 |
| 11 | 133919379 |
| 12 | 381516366 |
| 13 | 988173838 |
| 14 | 2446846672 |
| 15 | 5633359713 |
| 16 | 12527643860 |
| 17 | 26226659375 |
| 18 | 53655084387 |
| 19 | 104124710377 |
| 20 | 198817175068 |
| 21 | 363133886202 |
| 22 | 654527617329 |
[1,20,270,3000,23282,151473,768541,3422978, 12879078,44111410,133919379,381516366,988173838, 2446846672,5633359713,12527643860,26226659375, 53655084387,104124710377,198817175068, 363133886202,654527617329] |