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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 1 |
| 4 | 4 |
| 5 | 10 |
| 6 | 31 |
| 7 | 94 |
| 8 | 303 |
| 9 | 986 |
| 10 | 3284 |
| 11 | 11099 |
| 12 | 38024 |
| 13 | 131694 |
| 14 | 460607 |
| 15 | 1624451 |
| 16 | 5771532 |
| 17 | 20640334 |
| 18 | 74246701 |
| 19 | 268478962 |
| 20 | 975436348 |
| 21 | 3559204700 |
| 22 | 13037907692 |
| 23 | 47931423574 |
| 24 | 176792821643 |
| 25 | 654078238224 |
| 26 | 2426705590840 |
| 27 | 9026907769955 |
[1,0,1,1,4,10,31,94,303,986,3284,11099,38024, 131694,460607,1624451,5771532,20640334,74246701, 268478962,975436348,3559204700,13037907692, 47931423574,176792821643,654078238224, 2426705590840,9026907769955] |