| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 7 |
| 4 | 26 |
| 5 | 123 |
| 6 | 622 |
| 7 | 3490 |
| 8 | 20468 |
| 9 | 125643 |
| 10 | 792606 |
| 11 | 5118050 |
| 12 | 33612998 |
| 13 | 223770400 |
| 14 | 1505528080 |
| 15 | 10213807498 |
| 16 | 69746716716 |
| 17 | 478693572991 |
| 18 | 3298184837434 |
| 19 | 22790090901504 |
| 20 | 157803590073220 |
| 21 | 1094189186549354 |
| 22 | 7593267782966708 |
| 23 | 52713912426435111 |
| 24 | 365948276764762712 |
[1,1,2,7,26,123,622,3490,20468,125643,792606, 5118050,33612998,223770400,1505528080,10213807498, 69746716716,478693572991,3298184837434, 22790090901504,157803590073220,1094189186549354, 7593267782966708,52713912426435111, 365948276764762712] |