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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 7 |
| 3 | 55 |
| 4 | 427 |
| 5 | 3319 |
| 6 | 25795 |
| 7 | 200479 |
| 8 | 1558123 |
| 9 | 12109735 |
| 10 | 94116883 |
| 11 | 731476591 |
| 12 | 5685037435 |
| 13 | 44184121591 |
| 14 | 343399075747 |
| 15 | 2668898259775 |
| 16 | 20742682272907 |
| 17 | 161212165468999 |
| 18 | 1252941251920435 |
| 19 | 9737861756257039 |
| 20 | 75682679805321883 |
[0,1,7,55,427,3319,25795,200479,1558123,12109735, 94116883,731476591,5685037435,44184121591, 343399075747,2668898259775,20742682272907, 161212165468999,1252941251920435,9737861756257039, 75682679805321883] |