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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 12 |
| 3 | 36 |
| 4 | 100 |
| 5 | 300 |
| 6 | 776 |
| 7 | 2412 |
| 8 | 6304 |
| 9 | 19036 |
| 10 | 50952 |
| 11 | 148896 |
| 12 | 393452 |
| 13 | 1211444 |
| 14 | 3167004 |
| 15 | 9672772 |
| 16 | 25295248 |
| 17 | 76084796 |
| 18 | 200590424 |
| 19 | 608621376 |
| 20 | 1617201648 |
| 21 | 4908511140 |
| 22 | 12658776540 |
| 23 | 38907904188 |
| 24 | 102775961200 |
| 25 | 310485090044 |
[1,4,12,36,100,300,776,2412,6304,19036,50952, 148896,393452,1211444,3167004,9672772,25295248, 76084796,200590424,608621376,1617201648, 4908511140,12658776540,38907904188,102775961200, 310485090044] |