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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 0 |
| 3 | 1 |
| 4 | 6 |
| 5 | 38 |
| 6 | 274 |
| 7 | 2238 |
| 8 | 20462 |
| 9 | 207178 |
| 10 | 2301978 |
| 11 | 27853934 |
| 12 | 364633318 |
| 13 | 5135252562 |
| 14 | 77423807858 |
| 15 | 1244311197718 |
| 16 | 21236244441054 |
| 17 | 383579665216538 |
| 18 | 7310577148832842 |
| 19 | 146617686151591998 |
| 20 | 3086688129507199958 |
| 21 | 68061473255633759074 |
| 22 | 1568654907415559018658 |
[1,0,1,6,38,274,2238,20462,207178,2301978, 27853934,364633318,5135252562,77423807858, 1244311197718,21236244441054,383579665216538, 7310577148832842,146617686151591998, 3086688129507199958,68061473255633759074, 1568654907415559018658] |