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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 4 |
| 2 | 73 |
| 3 | 788 |
| 4 | 6630 |
| 5 | 48120 |
| 6 | 316526 |
| 7 | 1940568 |
| 8 | 11284380 |
| 9 | 62968560 |
| 10 | 339954670 |
| 11 | 1786320184 |
| 12 | 9176663028 |
| 13 | 46248446608 |
| 14 | 229285525420 |
| 15 | 1120646918000 |
| 16 | 5409322603896 |
| 17 | 25824570392544 |
| 18 | 122086747617198 |
| 19 | 572130452101240 |
| 20 | 2660063893120900 |
| 21 | 12279619924999504 |
| 22 | 56318986959592676 |
[0,4,73,788,6630,48120,316526,1940568,11284380, 62968560,339954670,1786320184,9176663028, 46248446608,229285525420,1120646918000, 5409322603896,25824570392544,122086747617198, 572130452101240,2660063893120900, 12279619924999504,56318986959592676] |