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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 12 |
| 3 | 109 |
| 4 | 888 |
| 5 | 6841 |
| 6 | 51012 |
| 7 | 372709 |
| 8 | 2687088 |
| 9 | 19200241 |
| 10 | 136354812 |
| 11 | 964249309 |
| 12 | 6798573288 |
| 13 | 47834153641 |
| 14 | 336059778612 |
| 15 | 2358521965909 |
| 16 | 16540171339488 |
| 17 | 115933787267041 |
| 18 | 812299450322412 |
| 19 | 5689910849522509 |
| 20 | 39848449432985688 |
[0,1,12,109,888,6841,51012,372709,2687088, 19200241,136354812,964249309,6798573288, 47834153641,336059778612,2358521965909, 16540171339488,115933787267041,812299450322412, 5689910849522509,39848449432985688] |