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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 16 |
| 5 | 45 |
| 6 | 142 |
| 7 | 459 |
| 8 | 1508 |
| 9 | 5122 |
| 10 | 17787 |
| 11 | 62649 |
| 12 | 223971 |
| 13 | 811339 |
| 14 | 2970032 |
| 15 | 10974150 |
| 16 | 40893393 |
| 17 | 153512844 |
| 18 | 580082454 |
| 19 | 2205046961 |
| 20 | 8427087958 |
| 21 | 32362949488 |
| 22 | 124837337235 |
| 23 | 483508287359 |
| 24 | 1879669861074 |
| 25 | 7332469937755 |
[1,1,2,6,16,45,142,459,1508,5122,17787,62649, 223971,811339,2970032,10974150,40893393,153512844, 580082454,2205046961,8427087958,32362949488, 124837337235,483508287359,1879669861074, 7332469937755] |