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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 7 |
| 5 | 25 |
| 6 | 102 |
| 7 | 531 |
| 8 | 3141 |
| 9 | 20218 |
| 10 | 146215 |
| 11 | 1174889 |
| 12 | 10225678 |
| 13 | 96226363 |
| 14 | 978420285 |
| 15 | 10657592850 |
| 16 | 123672458583 |
| 17 | 1525420453945 |
| 18 | 19929519469558 |
| 19 | 274771355003651 |
| 20 | 3987385414116085 |
| 21 | 60764250319690666 |
| 22 | 970085750385722631 |
| 23 | 16190361659675002857 |
[1,1,1,2,7,25,102,531,3141,20218,146215,1174889, 10225678,96226363,978420285,10657592850, 123672458583,1525420453945,19929519469558, 274771355003651,3987385414116085, 60764250319690666,970085750385722631, 16190361659675002857] |