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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 1 |
| 4 | 2 |
| 5 | 4 |
| 6 | 8 |
| 7 | 17 |
| 8 | 41 |
| 9 | 103 |
| 10 | 282 |
| 11 | 792 |
| 12 | 2239 |
| 13 | 6680 |
| 14 | 21143 |
| 15 | 70647 |
| 16 | 245357 |
| 17 | 871255 |
| 18 | 3202552 |
| 19 | 12334046 |
| 20 | 49635128 |
| 21 | 205403510 |
| 22 | 856780528 |
| 23 | 3601169551 |
| 24 | 15507530896 |
| 25 | 69267381313 |
| 26 | 320345619798 |
| 27 | 1518428936730 |
| 28 | 7345400773513 |
| 29 | 36469929240960 |
| 30 | 186875135258481 |
[1,0,1,1,2,4,8,17,41,103,282,792,2239,6680,21143, 70647,245357,871255,3202552,12334046,49635128, 205403510,856780528,3601169551,15507530896, 69267381313,320345619798,1518428936730, 7345400773513,36469929240960,186875135258481] |