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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 3 |
| 2 | 20 |
| 3 | 119 |
| 4 | 696 |
| 5 | 4059 |
| 6 | 23660 |
| 7 | 137903 |
| 8 | 803760 |
| 9 | 4684659 |
| 10 | 27304196 |
| 11 | 159140519 |
| 12 | 927538920 |
| 13 | 5406093003 |
| 14 | 31509019100 |
| 15 | 183648021599 |
| 16 | 1070379110496 |
| 17 | 6238626641379 |
| 18 | 36361380737780 |
| 19 | 211929657785303 |
| 20 | 1235216565974040 |
| 21 | 7199369738058939 |
| 22 | 41961001862379596 |
| 23 | 244566641436218639 |
[0,3,20,119,696,4059,23660,137903,803760,4684659, 27304196,159140519,927538920,5406093003, 31509019100,183648021599,1070379110496, 6238626641379,36361380737780,211929657785303, 1235216565974040,7199369738058939, 41961001862379596,244566641436218639] |