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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 26 |
| 5 | 142 |
| 6 | 930 |
| 7 | 7110 |
| 8 | 62138 |
| 9 | 610958 |
| 10 | 6674370 |
| 11 | 80201222 |
| 12 | 1051277530 |
| 13 | 14927729678 |
| 14 | 228262465634 |
| 15 | 3739557703366 |
| 16 | 65345926588026 |
| 17 | 1213197344607502 |
| 18 | 23848186328994178 |
| 19 | 494822251631023622 |
| 20 | 10807111342480752538 |
[1,1,2,6,26,142,930,7110,62138,610958,6674370, 80201222,1051277530,14927729678,228262465634, 3739557703366,65345926588026,1213197344607502, 23848186328994178,494822251631023622, 10807111342480752538] |