| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 64 |
| 5 | 1509 |
| 6 | 27589 |
| 7 | 453949 |
| 8 | 7116398 |
| 9 | 108922001 |
| 10 | 1646720185 |
| 11 | 24736055959 |
| 12 | 370331348806 |
| 13 | 5534979578369 |
| 14 | 82658873060821 |
| 15 | 1233993261692386 |
| 16 | 18420012632366897 |
| 17 | 274961514388882353 |
| 18 | 4104700898601864514 |
[1,1,2,64,1509,27589,453949,7116398,108922001, 1646720185,24736055959,370331348806,5534979578369, 82658873060821,1233993261692386,18420012632366897, 274961514388882353,4104700898601864514] |