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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 3 |
| 5 | 15 |
| 6 | 57 |
| 7 | 169 |
| 8 | 443 |
| 9 | 1211 |
| 10 | 3855 |
| 11 | 13495 |
| 12 | 46749 |
| 13 | 154397 |
| 14 | 496203 |
| 15 | 1611499 |
| 16 | 5395893 |
| 17 | 18473853 |
| 18 | 63472005 |
| 19 | 216711453 |
| 20 | 737070887 |
| 21 | 2515433411 |
| 22 | 8649866677 |
| 23 | 29935649141 |
| 24 | 103896813439 |
| 25 | 360791085751 |
| 26 | 1253684914707 |
| 27 | 4364603935363 |
[1,1,1,1,3,15,57,169,443,1211,3855,13495,46749, 154397,496203,1611499,5395893,18473853,63472005, 216711453,737070887,2515433411,8649866677, 29935649141,103896813439,360791085751, 1253684914707,4364603935363] |