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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 2 |
| 4 | 15 |
| 5 | 92 |
| 6 | 835 |
| 7 | 8322 |
| 8 | 99169 |
| 9 | 1325960 |
| 10 | 19966329 |
| 11 | 332259290 |
| 12 | 6070777999 |
| 13 | 120694673748 |
| 14 | 2594992240555 |
| 15 | 59986047422378 |
| 16 | 1483663965460545 |
| 17 | 39095051587497488 |
| 18 | 1093394763005554801 |
| 19 | 32347902448449172530 |
| 20 | 1009325655965539561231 |
| 21 | 33125674098690460236620 |
[1,0,1,2,15,92,835,8322,99169,1325960,19966329, 332259290,6070777999,120694673748,2594992240555, 59986047422378,1483663965460545,39095051587497488, 1093394763005554801,32347902448449172530, 1009325655965539561231,33125674098690460236620] |