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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 12 |
| 4 | 50 |
| 5 | 219 |
| 6 | 987 |
| 7 | 4552 |
| 8 | 21366 |
| 9 | 101730 |
| 10 | 490094 |
| 11 | 2384520 |
| 12 | 11699844 |
| 13 | 57825103 |
| 14 | 287611755 |
| 15 | 1438536144 |
| 16 | 7230782414 |
| 17 | 36506547918 |
| 18 | 185047345050 |
| 19 | 941359362760 |
| 20 | 4804468999932 |
| 21 | 24593960996814 |
| 22 | 126239765780606 |
| 23 | 649610643221616 |
| 24 | 3350542070046300 |
| 25 | 17318377059738820 |
[1,1,3,12,50,219,987,4552,21366,101730,490094, 2384520,11699844,57825103,287611755,1438536144, 7230782414,36506547918,185047345050,941359362760, 4804468999932,24593960996814,126239765780606, 649610643221616,3350542070046300, 17318377059738820] |