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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 16 |
| 3 | 64 |
| 4 | 248 |
| 5 | 944 |
| 6 | 3544 |
| 7 | 13168 |
| 8 | 48536 |
| 9 | 177776 |
| 10 | 647896 |
| 11 | 2351728 |
| 12 | 8508440 |
| 13 | 30701168 |
| 14 | 110537560 |
| 15 | 397266544 |
| 16 | 1425629336 |
| 17 | 5109684848 |
| 18 | 18295104472 |
| 19 | 65449056880 |
| 20 | 233970500888 |
| 21 | 835908980336 |
| 22 | 2984966034520 |
| 23 | 10654610339440 |
| 24 | 38017445912984 |
[4,16,64,248,944,3544,13168,48536,177776,647896, 2351728,8508440,30701168,110537560,397266544, 1425629336,5109684848,18295104472,65449056880, 233970500888,835908980336,2984966034520, 10654610339440,38017445912984] |