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| n | a(n) |
|---|---|
| 1 | 80 |
| 2 | 380 |
| 3 | 1776 |
| 4 | 8336 |
| 5 | 39084 |
| 6 | 183304 |
| 7 | 859628 |
| 8 | 4031428 |
| 9 | 18906220 |
| 10 | 88664800 |
| 11 | 415812536 |
| 12 | 1950042036 |
| 13 | 9145139904 |
| 14 | 42888093244 |
| 15 | 201132903028 |
| 16 | 943255846788 |
| 17 | 4423600410160 |
| 18 | 20745421993920 |
| 19 | 97290101680796 |
| 20 | 456262778740936 |
[80,380,1776,8336,39084,183304,859628,4031428, 18906220,88664800,415812536,1950042036,9145139904, 42888093244,201132903028,943255846788, 4423600410160,20745421993920,97290101680796, 456262778740936] |