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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 22 |
| 4 | 90 |
| 5 | 375 |
| 6 | 1632 |
| 7 | 7228 |
| 8 | 32542 |
| 9 | 148889 |
| 10 | 687558 |
| 11 | 3203532 |
| 12 | 15035292 |
| 13 | 70959865 |
| 14 | 336619928 |
| 15 | 1603694686 |
| 16 | 7667719866 |
| 17 | 36781517568 |
| 18 | 176929341895 |
| 19 | 853188421537 |
| 20 | 4123375152801 |
| 21 | 19966905610364 |
| 22 | 96858581103837 |
| 23 | 470608107771531 |
| 24 | 2289852607790047 |
| 25 | 11156510971249147 |
| 26 | 54421608462422660 |
| 27 | 265761980956092284 |
[1,2,6,22,90,375,1632,7228,32542,148889,687558, 3203532,15035292,70959865,336619928,1603694686, 7667719866,36781517568,176929341895,853188421537, 4123375152801,19966905610364,96858581103837, 470608107771531,2289852607790047, 11156510971249147,54421608462422660, 265761980956092284] |