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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 22 |
| 4 | 173 |
| 5 | 1816 |
| 6 | 23659 |
| 7 | 367573 |
| 8 | 6622465 |
| 9 | 135637477 |
| 10 | 3111148862 |
| 11 | 78984029782 |
| 12 | 2198423489832 |
| 13 | 66562555228478 |
| 14 | 2177861372888738 |
| 15 | 76571625673934064 |
| 16 | 2878937040339348981 |
| 17 | 115260759545001030638 |
| 18 | 4895471242828376133806 |
| 19 | 219853190410155476470763 |
[1,1,4,22,173,1816,23659,367573,6622465,135637477, 3111148862,78984029782,2198423489832, 66562555228478,2177861372888738,76571625673934064, 2878937040339348981,115260759545001030638, 4895471242828376133806,219853190410155476470763] |