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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 14 |
| 3 | 48 |
| 4 | 179 |
| 5 | 656 |
| 6 | 2394 |
| 7 | 8744 |
| 8 | 32791 |
| 9 | 123188 |
| 10 | 463211 |
| 11 | 1744076 |
| 12 | 6632688 |
| 13 | 25303978 |
| 14 | 96699766 |
| 15 | 370030836 |
| 16 | 1422210560 |
| 17 | 5479757300 |
| 18 | 21147107145 |
| 19 | 81707846148 |
| 20 | 316422360163 |
| 21 | 1227500661756 |
| 22 | 4768032430608 |
| 23 | 18539704936398 |
[1,4,14,48,179,656,2394,8744,32791,123188,463211, 1744076,6632688,25303978,96699766,370030836, 1422210560,5479757300,21147107145,81707846148, 316422360163,1227500661756,4768032430608, 18539704936398] |