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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 7 |
| 4 | 33 |
| 5 | 198 |
| 6 | 1432 |
| 7 | 12136 |
| 8 | 117772 |
| 9 | 1287718 |
| 10 | 15658052 |
| 11 | 209568126 |
| 12 | 3061140398 |
| 13 | 48454548452 |
| 14 | 826155841924 |
| 15 | 15094511153752 |
| 16 | 294206836405288 |
| 17 | 6093273074402848 |
| 18 | 133628182522968752 |
| 19 | 3093469935389714928 |
| 20 | 75384936371166307872 |
| 21 | 1928960833317580172688 |
[1,1,2,7,33,198,1432,12136,117772,1287718, 15658052,209568126,3061140398,48454548452, 826155841924,15094511153752,294206836405288, 6093273074402848,133628182522968752, 3093469935389714928,75384936371166307872, 1928960833317580172688] |