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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 11 |
| 4 | 31 |
| 5 | 88 |
| 6 | 250 |
| 7 | 710 |
| 8 | 2016 |
| 9 | 5724 |
| 10 | 16252 |
| 11 | 46144 |
| 12 | 131016 |
| 13 | 371992 |
| 14 | 1056192 |
| 15 | 2998832 |
| 16 | 8514544 |
| 17 | 24175232 |
| 18 | 68640416 |
| 19 | 194889824 |
| 20 | 553348096 |
| 21 | 1571113920 |
| 22 | 4460842944 |
| 23 | 12665612288 |
| 24 | 35961305216 |
| 25 | 102104457600 |
| 26 | 289903834112 |
[1,4,11,31,88,250,710,2016,5724,16252,46144, 131016,371992,1056192,2998832,8514544,24175232, 68640416,194889824,553348096,1571113920, 4460842944,12665612288,35961305216,102104457600, 289903834112] |