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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 18 |
| 5 | 57 |
| 6 | 198 |
| 7 | 709 |
| 8 | 2601 |
| 9 | 9864 |
| 10 | 38148 |
| 11 | 149808 |
| 12 | 598372 |
| 13 | 2419970 |
| 14 | 9889001 |
| 15 | 40838480 |
| 16 | 170083988 |
| 17 | 713613807 |
| 18 | 3015878875 |
| 19 | 12823991428 |
| 20 | 54829658278 |
| 21 | 235678930783 |
| 22 | 1017743418774 |
| 23 | 4413589486399 |
| 24 | 19218488856579 |
| 25 | 83989136588578 |
| 26 | 368284554761549 |
| 27 | 1620125911384969 |
| 28 | 7147971908460116 |
[1,1,2,6,18,57,198,709,2601,9864,38148,149808, 598372,2419970,9889001,40838480,170083988, 713613807,3015878875,12823991428,54829658278, 235678930783,1017743418774,4413589486399, 19218488856579,83989136588578,368284554761549, 1620125911384969,7147971908460116] |