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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 9 |
| 3 | 57 |
| 4 | 642 |
| 5 | 9402 |
| 6 | 177198 |
| 7 | 4051338 |
| 8 | 108926520 |
| 9 | 3371293704 |
| 10 | 118000461528 |
| 11 | 4609447152120 |
| 12 | 198791258476176 |
| 13 | 9381618706074768 |
| 14 | 480921576177145392 |
| 15 | 26610634173004959312 |
| 16 | 1580792845661466884352 |
| 17 | 100345182367660427554560 |
| 18 | 6778517964127816222982016 |
[1,3,9,57,642,9402,177198,4051338,108926520, 3371293704,118000461528,4609447152120, 198791258476176,9381618706074768, 480921576177145392,26610634173004959312, 1580792845661466884352,100345182367660427554560, 6778517964127816222982016] |