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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 1 |
| 4 | 18 |
| 5 | 3 |
| 6 | 926 |
| 7 | 264 |
| 8 | 146255 |
| 9 | 64190 |
| 10 | 138356840 |
| 11 | 22816773 |
| 12 | 509079790798 |
| 13 | 108923489863 |
| 14 | 6757117812676818 |
| 15 | 1403337110700033 |
| 16 | 474610323092906351464 |
| 17 | 52144014892723916074 |
| 18 | 130074987349483695192896881 |
| 19 | 14487112805054799566652854 |
| 20 | 132992779975091800967037313578152 |
[1,0,1,1,18,3,926,264,146255,64190,138356840, 22816773,509079790798,108923489863, 6757117812676818,1403337110700033, 474610323092906351464,52144014892723916074, 130074987349483695192896881, 14487112805054799566652854, 132992779975091800967037313578152] |