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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 4 |
| 2 | 39 |
| 3 | 235 |
| 4 | 235 |
| 5 | 12240 |
| 6 | 79468 |
| 7 | 667713 |
| 8 | 3961885 |
| 9 | 15491487 |
| 10 | 15491487 |
| 11 | 15491487 |
| 12 | 7924798459 |
| 13 | 77131234464 |
| 14 | 561576286499 |
| 15 | 4630914723593 |
| 16 | 23621160763365 |
| 17 | 189785813611370 |
| 18 | 1352938383547405 |
| 19 | 4609765579368303 |
| 20 | 4609765579368303 |
| 21 | 403571097067428308 |
[0,4,39,235,235,12240,79468,667713,3961885, 15491487,15491487,15491487,7924798459,77131234464, 561576286499,4630914723593,23621160763365, 189785813611370,1352938383547405,4609765579368303, 4609765579368303,403571097067428308] |