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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 11 |
| 4 | 42 |
| 5 | 154 |
| 6 | 612 |
| 7 | 2465 |
| 8 | 10171 |
| 9 | 42692 |
| 10 | 181338 |
| 11 | 780134 |
| 12 | 3384561 |
| 13 | 14814551 |
| 14 | 65278098 |
| 15 | 289414959 |
| 16 | 1290151950 |
| 17 | 5776944067 |
| 18 | 25982897662 |
| 19 | 117268906634 |
| 20 | 531182757836 |
| 21 | 2412943462536 |
| 22 | 10993079589220 |
| 23 | 50205601064387 |
| 24 | 229837749663298 |
| 25 | 1054413465243401 |
| 26 | 4846845454344601 |
| 27 | 22320844168428882 |
[1,1,4,11,42,154,612,2465,10171,42692,181338, 780134,3384561,14814551,65278098,289414959, 1290151950,5776944067,25982897662,117268906634, 531182757836,2412943462536,10993079589220, 50205601064387,229837749663298,1054413465243401, 4846845454344601,22320844168428882] |