| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 5 |
| 5 | 19 |
| 6 | 90 |
| 7 | 510 |
| 8 | 3395 |
| 9 | 25831 |
| 10 | 221140 |
| 11 | 2104310 |
| 12 | 22027170 |
| 13 | 251540795 |
| 14 | 3111928820 |
| 15 | 41460769350 |
| 16 | 591847005749 |
| 17 | 9011786683883 |
| 18 | 145794610986004 |
| 19 | 2497443795363566 |
| 20 | 45157627509568965 |
| 21 | 859494143391347310 |
| 22 | 17176870199851102510 |
| 23 | 359623890969235361700 |
[1,1,2,5,19,90,510,3395,25831,221140,2104310, 22027170,251540795,3111928820,41460769350, 591847005749,9011786683883,145794610986004, 2497443795363566,45157627509568965, 859494143391347310,17176870199851102510, 359623890969235361700] |