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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 57 |
| 3 | 474 |
| 4 | 3004 |
| 5 | 25773 |
| 6 | 215766 |
| 7 | 1669801 |
| 8 | 13333932 |
| 9 | 107746282 |
| 10 | 859595529 |
| 11 | 6863694378 |
| 12 | 54986385093 |
| 13 | 439924466026 |
| 14 | 3517929664756 |
| 15 | 28146676447417 |
| 16 | 225191238869774 |
| 17 | 1801425114687749 |
| 18 | 14411355379952868 |
| 19 | 115292842751246298 |
| 20 | 922338323835136341 |
[1,2,57,474,3004,25773,215766,1669801,13333932, 107746282,859595529,6863694378,54986385093, 439924466026,3517929664756,28146676447417, 225191238869774,1801425114687749, 14411355379952868,115292842751246298, 922338323835136341] |