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| n | a(n) |
|---|---|
| 0 | 4 |
| 1 | 0 |
| 2 | 18 |
| 3 | 48 |
| 4 | 294 |
| 5 | 1210 |
| 6 | 5508 |
| 7 | 23548 |
| 8 | 101614 |
| 9 | 433200 |
| 10 | 1845738 |
| 11 | 7840998 |
| 12 | 33282564 |
| 13 | 141149320 |
| 14 | 598366458 |
| 15 | 2535856048 |
| 16 | 10745092894 |
| 17 | 45524786370 |
| 18 | 192866785668 |
| 19 | 817050731748 |
| 20 | 3461224027254 |
| 21 | 14662350247600 |
| 22 | 62111682111618 |
| 23 | 263111844646798 |
| 24 | 1114566304573444 |
[4,0,18,48,294,1210,5508,23548,101614,433200, 1845738,7840998,33282564,141149320,598366458, 2535856048,10745092894,45524786370,192866785668, 817050731748,3461224027254,14662350247600, 62111682111618,263111844646798,1114566304573444] |