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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 20 |
| 2 | 140 |
| 3 | 620 |
| 4 | 2016 |
| 5 | 5364 |
| 6 | 12292 |
| 7 | 25228 |
| 8 | 47488 |
| 9 | 83508 |
| 10 | 138908 |
| 11 | 220748 |
| 12 | 337568 |
| 13 | 499668 |
| 14 | 719124 |
| 15 | 1010092 |
| 16 | 1388800 |
| 17 | 1873876 |
| 18 | 2486316 |
| 19 | 3249836 |
| 20 | 4190816 |
| 21 | 5338676 |
| 22 | 6725796 |
| 23 | 8387916 |
| 24 | 10364032 |
| 25 | 12696820 |
| 26 | 15432508 |
| 27 | 18621324 |
| 28 | 22317344 |
| 29 | 26578964 |
| 30 | 31468724 |
| 31 | 37053804 |
[1,20,140,620,2016,5364,12292,25228,47488,83508, 138908,220748,337568,499668,719124,1010092, 1388800,1873876,2486316,3249836,4190816,5338676, 6725796,8387916,10364032,12696820,15432508, 18621324,22317344,26578964,31468724,37053804] |