| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 4 |
| 4 | 34 |
| 5 | 65 |
| 6 | 2310 |
| 7 | 6272 |
| 8 | 1047424 |
| 9 | 3973536 |
| 10 | 3255714000 |
| 11 | 17050908600 |
| 12 | 69896096519040 |
| 13 | 501898385570868 |
| 14 | 10413963558878928048 |
| 15 | 102159685299672000000 |
| 16 | 10820560943026950635520000 |
| 17 | 144743469304894583259136000 |
| 18 | 78786195510356832343493745377280 |
[1,1,3,4,34,65,2310,6272,1047424,3973536, 3255714000,17050908600,69896096519040, 501898385570868,10413963558878928048, 102159685299672000000,10820560943026950635520000, 144743469304894583259136000, 78786195510356832343493745377280] |