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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 15 |
| 3 | 84 |
| 4 | 491 |
| 5 | 2948 |
| 6 | 18018 |
| 7 | 111520 |
| 8 | 696739 |
| 9 | 4384668 |
| 10 | 27753110 |
| 11 | 176494640 |
| 12 | 1126809230 |
| 13 | 7217773800 |
| 14 | 46364184420 |
| 15 | 298554038144 |
| 16 | 1926593569059 |
| 17 | 12455864623020 |
| 18 | 80664529969422 |
| 19 | 523165672201744 |
| 20 | 3397648036150426 |
| 21 | 22092460470618328 |
| 22 | 143809661629562460 |
[1,3,15,84,491,2948,18018,111520,696739,4384668, 27753110,176494640,1126809230,7217773800, 46364184420,298554038144,1926593569059, 12455864623020,80664529969422,523165672201744, 3397648036150426,22092460470618328, 143809661629562460] |