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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 12 |
| 2 | 156 |
| 3 | 2652 |
| 4 | 47580 |
| 5 | 835132 |
| 6 | 14274492 |
| 7 | 239210620 |
| 8 | 3954121852 |
| 9 | 64745687292 |
| 10 | 1053187674876 |
| 11 | 17052187400700 |
| 12 | 275180267037180 |
| 13 | 4430223031522300 |
| 14 | 71202253472533500 |
| 15 | 1142950923338418172 |
| 16 | 18330518457789188092 |
| 17 | 293793080103272648700 |
| 18 | 4706573484385846964220 |
[1,12,156,2652,47580,835132,14274492,239210620, 3954121852,64745687292,1053187674876, 17052187400700,275180267037180,4430223031522300, 71202253472533500,1142950923338418172, 18330518457789188092,293793080103272648700, 4706573484385846964220] |