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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 11 |
| 4 | 52 |
| 5 | 225 |
| 6 | 920 |
| 7 | 3695 |
| 8 | 14464 |
| 9 | 55593 |
| 10 | 210776 |
| 11 | 789995 |
| 12 | 2933380 |
| 13 | 10807625 |
| 14 | 39556316 |
| 15 | 143958335 |
| 16 | 521340016 |
| 17 | 1879901265 |
| 18 | 6753038624 |
| 19 | 24176722555 |
| 20 | 86294777316 |
| 21 | 307179518193 |
| 22 | 1090771084252 |
| 23 | 3864614381391 |
| 24 | 13664531314176 |
| 25 | 48225146757337 |
| 26 | 169905685271956 |
| 27 | 597661852713467 |
[1,4,11,52,225,920,3695,14464,55593,210776,789995, 2933380,10807625,39556316,143958335,521340016, 1879901265,6753038624,24176722555,86294777316, 307179518193,1090771084252,3864614381391, 13664531314176,48225146757337,169905685271956, 597661852713467] |