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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 21 |
| 5 | 76 |
| 6 | 275 |
| 7 | 989 |
| 8 | 3544 |
| 9 | 12696 |
| 10 | 45578 |
| 11 | 164194 |
| 12 | 593966 |
| 13 | 2158090 |
| 14 | 7875503 |
| 15 | 28862235 |
| 16 | 106203597 |
| 17 | 392291117 |
| 18 | 1454239837 |
| 19 | 5409048372 |
| 20 | 20182045236 |
| 21 | 75522431214 |
| 22 | 283377791271 |
| 23 | 1065990318403 |
| 24 | 4019415215923 |
| 25 | 15188857311110 |
| 26 | 57514327098488 |
| 27 | 218201177979480 |
| 28 | 829305547436095 |
[1,1,2,6,21,76,275,989,3544,12696,45578,164194, 593966,2158090,7875503,28862235,106203597, 392291117,1454239837,5409048372,20182045236, 75522431214,283377791271,1065990318403, 4019415215923,15188857311110,57514327098488, 218201177979480,829305547436095] |