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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 8 |
| 4 | 25 |
| 5 | 53 |
| 6 | 148 |
| 7 | 328 |
| 8 | 858 |
| 9 | 1938 |
| 10 | 4862 |
| 11 | 11066 |
| 12 | 27042 |
| 13 | 61662 |
| 14 | 147774 |
| 15 | 336854 |
| 16 | 795678 |
| 17 | 1810466 |
| 18 | 4228330 |
| 19 | 9597694 |
| 20 | 22211897 |
| 21 | 50279985 |
| 22 | 115489274 |
| 23 | 260686018 |
| 24 | 594986149 |
| 25 | 1339215285 |
| 26 | 3040004744 |
| 27 | 6823594396 |
| 28 | 15416270130 |
| 29 | 34510814918 |
| 30 | 77644149076 |
| 31 | 173368564396 |
[1,1,4,8,25,53,148,328,858,1938,4862,11066,27042, 61662,147774,336854,795678,1810466,4228330, 9597694,22211897,50279985,115489274,260686018, 594986149,1339215285,3040004744,6823594396, 15416270130,34510814918,77644149076,173368564396] |