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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 4 |
| 3 | 19 |
| 4 | 98 |
| 5 | 570 |
| 6 | 3642 |
| 7 | 25292 |
| 8 | 189454 |
| 9 | 1519648 |
| 10 | 12978141 |
| 11 | 117437020 |
| 12 | 1121299471 |
| 13 | 11256640012 |
| 14 | 118443403699 |
| 15 | 1302670531063 |
| 16 | 14938986954323 |
| 17 | 178248001223476 |
| 18 | 2208487163394749 |
| 19 | 28363722744050886 |
| 20 | 376991516806826090 |
| 21 | 5178009641895235269 |
| 22 | 73396161423153313320 |
[0,1,4,19,98,570,3642,25292,189454,1519648, 12978141,117437020,1121299471,11256640012, 118443403699,1302670531063,14938986954323, 178248001223476,2208487163394749, 28363722744050886,376991516806826090, 5178009641895235269,73396161423153313320] |