| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 9 |
| 4 | 54 |
| 5 | 392 |
| 6 | 3264 |
| 7 | 30375 |
| 8 | 311482 |
| 9 | 3492134 |
| 10 | 42613740 |
| 11 | 564395954 |
| 12 | 8094807168 |
| 13 | 125423821396 |
| 14 | 2093539627292 |
| 15 | 37521869868373 |
| 16 | 719483654260090 |
| 17 | 14705046942685816 |
| 18 | 319171681858506880 |
| 19 | 7331367124418082012 |
| 20 | 177646903957002411656 |
| 21 | 4527740283395695051578 |
[1,1,2,9,54,392,3264,30375,311482,3492134, 42613740,564395954,8094807168,125423821396, 2093539627292,37521869868373,719483654260090, 14705046942685816,319171681858506880, 7331367124418082012,177646903957002411656, 4527740283395695051578] |