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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 15 |
| 4 | 58 |
| 5 | 215 |
| 6 | 789 |
| 7 | 2850 |
| 8 | 10219 |
| 9 | 36330 |
| 10 | 128383 |
| 11 | 450997 |
| 12 | 1576384 |
| 13 | 5484086 |
| 14 | 18997492 |
| 15 | 65547958 |
| 16 | 225329592 |
| 17 | 771920515 |
| 18 | 2635815051 |
| 19 | 8972752531 |
| 20 | 30456389557 |
| 21 | 103095375148 |
| 22 | 348071445217 |
| 23 | 1172252449310 |
| 24 | 3938655968745 |
| 25 | 13203699803684 |
| 26 | 44167916497886 |
| 27 | 147442143911193 |
| 28 | 491220771388477 |
[1,1,4,15,58,215,789,2850,10219,36330,128383, 450997,1576384,5484086,18997492,65547958, 225329592,771920515,2635815051,8972752531, 30456389557,103095375148,348071445217, 1172252449310,3938655968745,13203699803684, 44167916497886,147442143911193,491220771388477] |