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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 7 |
| 3 | 50 |
| 4 | 397 |
| 5 | 3366 |
| 6 | 29197 |
| 7 | 253030 |
| 8 | 2170357 |
| 9 | 18385046 |
| 10 | 153927037 |
| 11 | 1275981510 |
| 12 | 10492253317 |
| 13 | 85727548726 |
| 14 | 696964520077 |
| 15 | 5644579061990 |
| 16 | 45579645264277 |
| 17 | 367223771048406 |
| 18 | 2953549834748317 |
| 19 | 23724145930814470 |
| 20 | 190373553357763237 |
[0,1,7,50,397,3366,29197,253030,2170357,18385046, 153927037,1275981510,10492253317,85727548726, 696964520077,5644579061990,45579645264277, 367223771048406,2953549834748317, 23724145930814470,190373553357763237] |