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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 4 |
| 4 | 25 |
| 5 | 108 |
| 6 | 788 |
| 7 | 4740 |
| 8 | 44445 |
| 9 | 339632 |
| 10 | 3625136 |
| 11 | 35508536 |
| 12 | 462626736 |
| 13 | 5273725108 |
| 14 | 76634997096 |
| 15 | 1047347436984 |
| 16 | 17542238923677 |
| 17 | 268193251446228 |
| 18 | 4949536256552648 |
| 19 | 86303019303031400 |
| 20 | 1768833677916545596 |
| 21 | 34165810747993948664 |
| 22 | 759192269597947084836 |
[0,0,1,4,25,108,788,4740,44445,339632,3625136, 35508536,462626736,5273725108,76634997096, 1047347436984,17542238923677,268193251446228, 4949536256552648,86303019303031400, 1768833677916545596,34165810747993948664, 759192269597947084836] |