| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 4 |
| 3 | 50 |
| 4 | 98 |
| 5 | 1830 |
| 6 | 7264 |
| 7 | 89326 |
| 8 | 247252 |
| 9 | 4520886 |
| 10 | 20225372 |
| 11 | 241414342 |
| 12 | 786393322 |
| 13 | 12744704970 |
| 14 | 62688642800 |
| 15 | 771140700226 |
| 16 | 2635449405522 |
| 17 | 40907909552038 |
| 18 | 211134761381948 |
| 19 | 2451388697035478 |
| 20 | 9148627707018230 |
| 21 | 143396849321918482 |
| 22 | 743716982801639120 |
[1,2,4,50,98,1830,7264,89326,247252,4520886, 20225372,241414342,786393322,12744704970, 62688642800,771140700226,2635449405522, 40907909552038,211134761381948,2451388697035478, 9148627707018230,143396849321918482, 743716982801639120] |