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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 18 |
| 3 | 108 |
| 4 | 180 |
| 5 | 270 |
| 6 | 810 |
| 7 | 4158 |
| 8 | 4968 |
| 9 | 5850 |
| 10 | 7308 |
| 11 | 10710 |
| 12 | 13338 |
| 13 | 17028 |
| 14 | 26730 |
| 15 | 32940 |
| 16 | 38610 |
| 17 | 70488 |
| 18 | 72090 |
| 19 | 102078 |
| 20 | 117990 |
| 21 | 122148 |
| 22 | 128520 |
| 23 | 132858 |
| 24 | 153270 |
| 25 | 228960 |
| 26 | 231840 |
| 27 | 240588 |
| 28 | 246510 |
| 29 | 249498 |
| 30 | 296478 |
| 31 | 326610 |
| 32 | 372708 |
| 33 | 391248 |
| 34 | 417960 |
| 35 | 429678 |
| 36 | 449568 |
| 37 | 453600 |
[4,18,108,180,270,810,4158,4968,5850,7308,10710, 13338,17028,26730,32940,38610,70488,72090,102078, 117990,122148,128520,132858,153270,228960,231840, 240588,246510,249498,296478,326610,372708,391248, 417960,429678,449568,453600] |