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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 23 |
| 5 | 156 |
| 6 | 1162 |
| 7 | 9192 |
| 8 | 75819 |
| 9 | 644908 |
| 10 | 5616182 |
| 11 | 49826712 |
| 12 | 448771622 |
| 13 | 4092553752 |
| 14 | 37714212564 |
| 15 | 350658882768 |
| 16 | 3285490743987 |
| 17 | 30989950019532 |
| 18 | 294031964658430 |
| 19 | 2804331954047160 |
| 20 | 26870823304476690 |
| 21 | 258548658860327880 |
[1,1,4,23,156,1162,9192,75819,644908,5616182, 49826712,448771622,4092553752,37714212564, 350658882768,3285490743987,30989950019532, 294031964658430,2804331954047160, 26870823304476690,258548658860327880] |