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| n | a(n) |
|---|---|
| 2 | 1 |
| 3 | 4 |
| 4 | 10 |
| 5 | 58 |
| 6 | 178 |
| 7 | 1258 |
| 8 | 2280 |
| 9 | 7558 |
| 10 | 37798 |
| 11 | 415798 |
| 12 | 1229760 |
| 13 | 16144536 |
| 14 | 113488440 |
| 15 | 567495336 |
| 16 | 1135133998 |
| 17 | 19295619336 |
| 18 | 56915913600 |
| 19 | 1085995965600 |
| 20 | 5499724229998 |
| 21 | 37888326510336 |
| 22 | 423202615117920 |
| 23 | 9425816095466520 |
| 24 | 29220034833989998 |
| 25 | 146100157813443360 |
| 26 | 1882777893068160000 |
| 27 | 5683471349506454400 |
| 28 | 39885027849235856880 |
[1,4,10,58,178,1258,2280,7558,37798,415798, 1229760,16144536,113488440,567495336,1135133998, 19295619336,56915913600,1085995965600, 5499724229998,37888326510336,423202615117920, 9425816095466520,29220034833989998, 146100157813443360,1882777893068160000, 5683471349506454400,39885027849235856880] |