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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 22 |
| 4 | 139 |
| 5 | 953 |
| 6 | 6894 |
| 7 | 51796 |
| 8 | 400269 |
| 9 | 3161262 |
| 10 | 25403536 |
| 11 | 207043048 |
| 12 | 1707345547 |
| 13 | 14219399626 |
| 14 | 119431172630 |
| 15 | 1010495472960 |
| 16 | 8604568715969 |
| 17 | 73683710894255 |
| 18 | 634142349130800 |
| 19 | 5482062214763436 |
| 20 | 47582484748270453 |
| 21 | 414503778412715065 |
| 22 | 3622792181209018168 |
| 23 | 31758958747482608912 |
[1,1,4,22,139,953,6894,51796,400269,3161262, 25403536,207043048,1707345547,14219399626, 119431172630,1010495472960,8604568715969, 73683710894255,634142349130800,5482062214763436, 47582484748270453,414503778412715065, 3622792181209018168,31758958747482608912] |