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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 16 |
| 3 | 70 |
| 4 | 322 |
| 5 | 1498 |
| 6 | 7094 |
| 7 | 34036 |
| 8 | 164048 |
| 9 | 796202 |
| 10 | 3885290 |
| 11 | 19002928 |
| 12 | 93264752 |
| 13 | 459007438 |
| 14 | 2262036586 |
| 15 | 11169376970 |
| 16 | 55240445346 |
| 17 | 273433650434 |
| 18 | 1355096702100 |
| 19 | 6722446090996 |
| 20 | 33368104779532 |
| 21 | 165759411164920 |
| 22 | 823978800776782 |
| 23 | 4097584417473362 |
| 24 | 20387964048849642 |
| 25 | 101489536218814760 |
[1,4,16,70,322,1498,7094,34036,164048,796202, 3885290,19002928,93264752,459007438,2262036586, 11169376970,55240445346,273433650434, 1355096702100,6722446090996,33368104779532, 165759411164920,823978800776782,4097584417473362, 20387964048849642,101489536218814760] |