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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 3 |
| 4 | 9 |
| 5 | 20 |
| 6 | 75 |
| 7 | 262 |
| 8 | 1117 |
| 9 | 4783 |
| 10 | 21971 |
| 11 | 102249 |
| 12 | 489077 |
| 13 | 2370142 |
| 14 | 11654465 |
| 15 | 57916324 |
| 16 | 290693391 |
| 17 | 1471341341 |
| 18 | 7504177738 |
| 19 | 38532692207 |
| 20 | 199076194985 |
| 21 | 1034236705992 |
| 22 | 5400337050086 |
| 23 | 28329240333758 |
| 24 | 149244907249629 |
[1,1,2,3,9,20,75,262,1117,4783,21971,102249, 489077,2370142,11654465,57916324,290693391, 1471341341,7504177738,38532692207,199076194985, 1034236705992,5400337050086,28329240333758, 149244907249629] |