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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 6 |
| 3 | 35 |
| 4 | 240 |
| 5 | 2077 |
| 6 | 23562 |
| 7 | 358775 |
| 8 | 7449060 |
| 9 | 213188689 |
| 10 | 8473977534 |
| 11 | 470309723435 |
| 12 | 36582636406680 |
| 13 | 3998655357260293 |
| 14 | 615328930033081458 |
| 15 | 133485330929459963615 |
| 16 | 40859530900982506959180 |
| 17 | 17659495180812130332490681 |
| 18 | 10781678259164073608877557286 |
| 19 | 9301770545157096607562560360595 |
[0,1,6,35,240,2077,23562,358775,7449060,213188689, 8473977534,470309723435,36582636406680, 3998655357260293,615328930033081458, 133485330929459963615,40859530900982506959180, 17659495180812130332490681, 10781678259164073608877557286, 9301770545157096607562560360595] |