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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 21 |
| 5 | 131 |
| 6 | 943 |
| 7 | 7701 |
| 8 | 70409 |
| 9 | 712891 |
| 10 | 7921011 |
| 11 | 95844233 |
| 12 | 1254688141 |
| 13 | 17670191319 |
| 14 | 266412115271 |
| 15 | 4281623281141 |
| 16 | 73073037331473 |
| 17 | 1319881736799731 |
| 18 | 25155393101359579 |
| 19 | 504505383866156001 |
| 20 | 10621165976129600021 |
| 21 | 234196709773657680463 |
| 22 | 5397676549069062730671 |
[1,1,1,4,21,131,943,7701,70409,712891,7921011, 95844233,1254688141,17670191319,266412115271, 4281623281141,73073037331473,1319881736799731, 25155393101359579,504505383866156001, 10621165976129600021,234196709773657680463, 5397676549069062730671] |