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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 4 |
| 3 | 10 |
| 4 | 40 |
| 5 | 278 |
| 6 | 3554 |
| 7 | 84590 |
| 8 | 3776280 |
| 9 | 317806466 |
| 10 | 50710452574 |
| 11 | 15414839551538 |
| 12 | 8964708979273634 |
| 13 | 10008446308186072290 |
| 14 | 21518891146915893435358 |
| 15 | 89320970210116481106835986 |
| 16 | 717558285660687970023516336792 |
| 17 | 11176382741327158622885664697124082 |
| 18 | 338202509574712032788035618665293979610 |
[1,2,4,10,40,278,3554,84590,3776280,317806466, 50710452574,15414839551538,8964708979273634, 10008446308186072290,21518891146915893435358, 89320970210116481106835986, 717558285660687970023516336792, 11176382741327158622885664697124082, 338202509574712032788035618665293979610] |