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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 33 |
| 3 | 120 |
| 4 | 534 |
| 5 | 2976 |
| 6 | 13759 |
| 7 | 65009 |
| 8 | 325008 |
| 9 | 1565481 |
| 10 | 7539236 |
| 11 | 36795842 |
| 12 | 178342390 |
| 13 | 863486059 |
| 14 | 4193371665 |
| 15 | 20339714386 |
| 16 | 98614688025 |
| 17 | 478433693926 |
| 18 | 2320695414662 |
| 19 | 11255335524904 |
| 20 | 54595627967873 |
| 21 | 264817091402701 |
| 22 | 1284455883761926 |
[4,33,120,534,2976,13759,65009,325008,1565481, 7539236,36795842,178342390,863486059,4193371665, 20339714386,98614688025,478433693926, 2320695414662,11255335524904,54595627967873, 264817091402701,1284455883761926] |