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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 12 |
| 3 | 36 |
| 4 | 92 |
| 5 | 252 |
| 6 | 628 |
| 7 | 1644 |
| 8 | 4052 |
| 9 | 10340 |
| 10 | 25332 |
| 11 | 63708 |
| 12 | 155452 |
| 13 | 387036 |
| 14 | 941948 |
| 15 | 2328740 |
| 16 | 5657236 |
| 17 | 13914596 |
| 18 | 33757804 |
| 19 | 82713164 |
| 20 | 200467108 |
| 21 | 489746916 |
| 22 | 1186060492 |
| 23 | 2891000036 |
| 24 | 6997192716 |
| 25 | 17025058164 |
| 26 | 41186981772 |
| 27 | 100070851212 |
| 28 | 242000513660 |
| 29 | 587312389940 |
[1,4,12,36,92,252,628,1644,4052,10340,25332,63708, 155452,387036,941948,2328740,5657236,13914596, 33757804,82713164,200467108,489746916,1186060492, 2891000036,6997192716,17025058164,41186981772, 100070851212,242000513660,587312389940] |