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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 4 |
| 3 | 47 |
| 4 | 395 |
| 5 | 3453 |
| 6 | 30475 |
| 7 | 268257 |
| 8 | 2360984 |
| 9 | 20781746 |
| 10 | 182923358 |
| 11 | 1610107387 |
| 12 | 14172312272 |
| 13 | 124745996060 |
| 14 | 1098025707095 |
| 15 | 9664923050975 |
| 16 | 85071539806558 |
| 17 | 748807501780793 |
| 18 | 6591072360831728 |
| 19 | 58015223889383283 |
| 20 | 510655325670196475 |
[0,4,47,395,3453,30475,268257,2360984,20781746, 182923358,1610107387,14172312272,124745996060, 1098025707095,9664923050975,85071539806558, 748807501780793,6591072360831728, 58015223889383283,510655325670196475] |