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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 32 |
| 3 | 160 |
| 4 | 852 |
| 5 | 4232 |
| 6 | 21020 |
| 7 | 102652 |
| 8 | 497720 |
| 9 | 2397844 |
| 10 | 11501012 |
| 11 | 54967576 |
| 12 | 261998092 |
| 13 | 1245969948 |
| 14 | 5913866044 |
| 15 | 28021308344 |
| 16 | 132570243968 |
| 17 | 626365075348 |
| 18 | 2956008677160 |
[1,4,32,160,852,4232,21020,102652,497720,2397844, 11501012,54967576,261998092,1245969948,5913866044, 28021308344,132570243968,626365075348, 2956008677160] |