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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 6 |
| 3 | 72 |
| 4 | 600 |
| 5 | 4607 |
| 6 | 31669 |
| 7 | 208949 |
| 8 | 1324269 |
| 9 | 8152245 |
| 10 | 49070731 |
| 11 | 289979290 |
| 12 | 1687730558 |
| 13 | 9698213032 |
| 14 | 55123714128 |
| 15 | 310376329220 |
| 16 | 1733254750248 |
| 17 | 9609161226263 |
| 18 | 52931141892017 |
| 19 | 289892095063747 |
| 20 | 1579473182908079 |
[0,6,72,600,4607,31669,208949,1324269,8152245, 49070731,289979290,1687730558,9698213032, 55123714128,310376329220,1733254750248, 9609161226263,52931141892017,289892095063747, 1579473182908079] |