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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 88 |
| 6 | 303 |
| 7 | 1033 |
| 8 | 3544 |
| 9 | 12220 |
| 10 | 42164 |
| 11 | 145364 |
| 12 | 500954 |
| 13 | 1726408 |
| 14 | 5950050 |
| 15 | 20507364 |
| 16 | 70680192 |
| 17 | 243602952 |
| 18 | 839588620 |
| 19 | 2893682172 |
| 20 | 9973219220 |
| 21 | 34373198420 |
| 22 | 118468937648 |
| 23 | 408309065104 |
| 24 | 1407257423576 |
| 25 | 4850182474912 |
[1,1,2,6,24,88,303,1033,3544,12220,42164,145364, 500954,1726408,5950050,20507364,70680192, 243602952,839588620,2893682172,9973219220, 34373198420,118468937648,408309065104, 1407257423576,4850182474912] |