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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 20 |
| 4 | 70 |
| 5 | 254 |
| 6 | 942 |
| 7 | 3550 |
| 8 | 13532 |
| 9 | 52030 |
| 10 | 201386 |
| 11 | 783560 |
| 12 | 3061442 |
| 13 | 12001804 |
| 14 | 47181278 |
| 15 | 185904220 |
| 16 | 733908634 |
| 17 | 2901998092 |
| 18 | 11490757796 |
| 19 | 45552262860 |
| 20 | 180762964146 |
| 21 | 717939220774 |
| 22 | 2853611232902 |
| 23 | 11349816190552 |
| 24 | 45168339253888 |
| 25 | 179845805435900 |
| 26 | 716409551285034 |
| 27 | 2854926106932244 |
[1,2,6,20,70,254,942,3550,13532,52030,201386, 783560,3061442,12001804,47181278,185904220, 733908634,2901998092,11490757796,45552262860, 180762964146,717939220774,2853611232902, 11349816190552,45168339253888,179845805435900, 716409551285034,2854926106932244] |