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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 22 |
| 5 | 184 |
| 6 | 2278 |
| 7 | 37076 |
| 8 | 747830 |
| 9 | 17938120 |
| 10 | 498221046 |
| 11 | 15716127456 |
| 12 | 554857740936 |
| 13 | 21672428437044 |
| 14 | 927792029298550 |
| 15 | 43195423181912812 |
| 16 | 2172838098801762500 |
| 17 | 117433517088859845912 |
| 18 | 6786305674234003471552 |
| 19 | 417560119759063983102136 |
| 20 | 27254276361313006814819076 |
[1,1,2,4,22,184,2278,37076,747830,17938120, 498221046,15716127456,554857740936,21672428437044, 927792029298550,43195423181912812, 2172838098801762500,117433517088859845912, 6786305674234003471552,417560119759063983102136, 27254276361313006814819076] |