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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 6 |
| 4 | 15 |
| 5 | 33 |
| 6 | 84 |
| 7 | 203 |
| 8 | 525 |
| 9 | 1330 |
| 10 | 3465 |
| 11 | 8955 |
| 12 | 23400 |
| 13 | 60957 |
| 14 | 159471 |
| 15 | 416702 |
| 16 | 1090635 |
| 17 | 2853229 |
| 18 | 7469052 |
| 19 | 19548759 |
| 20 | 51177225 |
| 21 | 133969386 |
| 22 | 350730933 |
| 23 | 918187991 |
| 24 | 2403833040 |
| 25 | 6293218393 |
| 26 | 16475822139 |
| 27 | 43134005238 |
[1,3,6,15,33,84,203,525,1330,3465,8955,23400, 60957,159471,416702,1090635,2853229,7469052, 19548759,51177225,133969386,350730933,918187991, 2403833040,6293218393,16475822139,43134005238] |