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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 25 |
| 5 | 122 |
| 6 | 726 |
| 7 | 5064 |
| 8 | 40441 |
| 9 | 363603 |
| 10 | 3633852 |
| 11 | 39957180 |
| 12 | 479364841 |
| 13 | 6230652124 |
| 14 | 87218228180 |
| 15 | 1308153551160 |
| 16 | 20929018724041 |
| 17 | 355774626352325 |
| 18 | 6403681619657310 |
| 19 | 121666026312835410 |
| 20 | 2433257739200536081 |
| 21 | 51097345199332200726 |
| 22 | 1124122383340449444042 |
[1,1,2,6,25,122,726,5064,40441,363603,3633852, 39957180,479364841,6230652124,87218228180, 1308153551160,20929018724041,355774626352325, 6403681619657310,121666026312835410, 2433257739200536081,51097345199332200726, 1124122383340449444042] |