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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 20 |
| 2 | 225 |
| 3 | 1882 |
| 4 | 13070 |
| 5 | 79872 |
| 6 | 444902 |
| 7 | 2311828 |
| 8 | 11388999 |
| 9 | 53820068 |
| 10 | 246112783 |
| 11 | 1096379070 |
| 12 | 4782801180 |
| 13 | 20515294320 |
| 14 | 86808499020 |
| 15 | 363304109640 |
| 16 | 1507010836605 |
| 17 | 6206407299540 |
| 18 | 25412183425165 |
| 19 | 103563957886370 |
[1,20,225,1882,13070,79872,444902,2311828, 11388999,53820068,246112783,1096379070,4782801180, 20515294320,86808499020,363304109640, 1507010836605,6206407299540,25412183425165, 103563957886370] |