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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 2 |
| 3 | 18 |
| 4 | 146 |
| 5 | 1170 |
| 6 | 9362 |
| 7 | 74898 |
| 8 | 599186 |
| 9 | 4793490 |
| 10 | 38347922 |
| 11 | 306783378 |
| 12 | 2454267026 |
| 13 | 19634136210 |
| 14 | 157073089682 |
| 15 | 1256584717458 |
| 16 | 10052677739666 |
| 17 | 80421421917330 |
| 18 | 643371375338642 |
| 19 | 5146971002709138 |
| 20 | 41175768021673106 |
| 21 | 329406144173384850 |
| 22 | 2635249153387078802 |
| 23 | 21081993227096630418 |
[0,2,18,146,1170,9362,74898,599186,4793490, 38347922,306783378,2454267026,19634136210, 157073089682,1256584717458,10052677739666, 80421421917330,643371375338642,5146971002709138, 41175768021673106,329406144173384850, 2635249153387078802,21081993227096630418] |