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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 17 |
| 4 | 96 |
| 5 | 595 |
| 6 | 4516 |
| 7 | 37104 |
| 8 | 351020 |
| 9 | 3604001 |
| 10 | 41007240 |
| 11 | 502039444 |
| 12 | 6703536516 |
| 13 | 95376507135 |
| 14 | 1459072099824 |
| 15 | 23677731306350 |
| 16 | 408821193129564 |
| 17 | 7443839953433701 |
| 18 | 143258713990271960 |
| 19 | 2893053522512463984 |
| 20 | 61396438056305204020 |
| 21 | 1362146168353191078195 |
| 22 | 31605702195327725326560 |
[1,1,4,17,96,595,4516,37104,351020,3604001, 41007240,502039444,6703536516,95376507135, 1459072099824,23677731306350,408821193129564, 7443839953433701,143258713990271960, 2893053522512463984,61396438056305204020, 1362146168353191078195,31605702195327725326560] |