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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 6 |
| 3 | 54 |
| 4 | 438 |
| 5 | 3510 |
| 6 | 28086 |
| 7 | 224694 |
| 8 | 1797558 |
| 9 | 14380470 |
| 10 | 115043766 |
| 11 | 920350134 |
| 12 | 7362801078 |
| 13 | 58902408630 |
| 14 | 471219269046 |
| 15 | 3769754152374 |
| 16 | 30158033218998 |
| 17 | 241264265751990 |
| 18 | 1930114126015926 |
| 19 | 15440913008127414 |
| 20 | 123527304065019318 |
| 21 | 988218432520154550 |
| 22 | 7905747460161236406 |
[0,6,54,438,3510,28086,224694,1797558,14380470, 115043766,920350134,7362801078,58902408630, 471219269046,3769754152374,30158033218998, 241264265751990,1930114126015926, 15440913008127414,123527304065019318, 988218432520154550,7905747460161236406] |