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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 18 |
| 3 | 42 |
| 4 | 346 |
| 5 | 1767 |
| 6 | 10182 |
| 7 | 60352 |
| 8 | 350540 |
| 9 | 2034140 |
| 10 | 11908298 |
| 11 | 69366367 |
| 12 | 404422900 |
| 13 | 2359475306 |
| 14 | 13758737304 |
| 15 | 80237613315 |
| 16 | 467966274418 |
| 17 | 2729123464612 |
| 18 | 15916133452018 |
| 19 | 92823028361780 |
| 20 | 541340687856998 |
| 21 | 3157085468272805 |
[0,18,42,346,1767,10182,60352,350540,2034140, 11908298,69366367,404422900,2359475306, 13758737304,80237613315,467966274418, 2729123464612,15916133452018,92823028361780, 541340687856998,3157085468272805] |