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| n | a(n) |
|---|---|
| 1 | 18 |
| 2 | 324 |
| 3 | 1350 |
| 4 | 5625 |
| 5 | 15525 |
| 6 | 42849 |
| 7 | 95220 |
| 8 | 211600 |
| 9 | 409860 |
| 10 | 793881 |
| 11 | 1397088 |
| 12 | 2458624 |
| 13 | 4029760 |
| 14 | 6604900 |
| 15 | 10246590 |
| 16 | 15896169 |
| 17 | 23603040 |
| 18 | 35046400 |
| 19 | 50207520 |
| 20 | 71927361 |
| 21 | 100016433 |
| 22 | 139074849 |
| 23 | 188570070 |
| 24 | 255680100 |
| 25 | 339259830 |
| 26 | 450161089 |
| 27 | 586225710 |
[18,324,1350,5625,15525,42849,95220,211600,409860, 793881,1397088,2458624,4029760,6604900,10246590, 15896169,23603040,35046400,50207520,71927361, 100016433,139074849,188570070,255680100,339259830, 450161089,586225710] |