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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 4 |
| 4 | 24 |
| 5 | 54 |
| 6 | 35 |
| 7 | 356 |
| 8 | 1044 |
| 9 | 1488 |
| 10 | 604 |
| 11 | 16585 |
| 12 | 31620 |
| 13 | 60900 |
| 14 | 57900 |
| 15 | 16727 |
| 16 | 3461916 |
| 17 | 1699290 |
| 18 | 3345420 |
| 19 | 4744380 |
| 20 | 3128880 |
| 21 | 681232 |
| 22 | 6058301508 |
| 23 | 265521354 |
| 24 | 263429355 |
| 25 | 439698420 |
| 26 | 455785470 |
| 27 | 222132666 |
| 28 | 38187291 |
[1,4,4,24,54,35,356,1044,1488,604,16585,31620, 60900,57900,16727,3461916,1699290,3345420,4744380, 3128880,681232,6058301508,265521354,263429355, 439698420,455785470,222132666,38187291] |