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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 16 |
| 3 | 52 |
| 4 | 160 |
| 5 | 452 |
| 6 | 1232 |
| 7 | 3204 |
| 8 | 8112 |
| 9 | 19956 |
| 10 | 48112 |
| 11 | 113732 |
| 12 | 264816 |
| 13 | 607876 |
| 14 | 1379264 |
| 15 | 3096372 |
| 16 | 6888784 |
| 17 | 15201156 |
| 18 | 33306752 |
| 19 | 72510916 |
| 20 | 156972960 |
| 21 | 338089844 |
| 22 | 724883552 |
| 23 | 1547816708 |
| 24 | 3292816416 |
| 25 | 6981664708 |
| 26 | 14758159472 |
| 27 | 31110217524 |
| 28 | 65415167744 |
| 29 | 137230388228 |
[1,4,16,52,160,452,1232,3204,8112,19956,48112, 113732,264816,607876,1379264,3096372,6888784, 15201156,33306752,72510916,156972960,338089844, 724883552,1547816708,3292816416,6981664708, 14758159472,31110217524,65415167744,137230388228] |