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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 7 |
| 3 | 33 |
| 4 | 198 |
| 5 | 1453 |
| 6 | 12669 |
| 7 | 128320 |
| 8 | 1482721 |
| 9 | 19260421 |
| 10 | 277913552 |
| 11 | 4410640919 |
| 12 | 76360030701 |
| 13 | 1432144732762 |
| 14 | 28926138244883 |
| 15 | 625974400305541 |
| 16 | 14449445989893990 |
| 17 | 354384475357492593 |
| 18 | 9202837263156670345 |
| 19 | 252260867710562944224 |
| 20 | 7278710072406887897461 |
[1,2,7,33,198,1453,12669,128320,1482721,19260421, 277913552,4410640919,76360030701,1432144732762, 28926138244883,625974400305541,14449445989893990, 354384475357492593,9202837263156670345, 252260867710562944224,7278710072406887897461] |