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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 13 |
| 5 | 53 |
| 6 | 199 |
| 7 | 674 |
| 8 | 2313 |
| 9 | 8731 |
| 10 | 34453 |
| 11 | 135151 |
| 12 | 516056 |
| 13 | 1929917 |
| 14 | 7191767 |
| 15 | 27150041 |
| 16 | 104424657 |
| 17 | 407094655 |
| 18 | 1594363303 |
| 19 | 6233521880 |
| 20 | 24277356505 |
| 21 | 94261319494 |
| 22 | 365585759896 |
| 23 | 1419238266986 |
| 24 | 5523689999096 |
| 25 | 21573875791838 |
| 26 | 84572021687714 |
| 27 | 332542322089642 |
| 28 | 1309933674885610 |
[1,1,4,13,53,199,674,2313,8731,34453,135151, 516056,1929917,7191767,27150041,104424657, 407094655,1594363303,6233521880,24277356505, 94261319494,365585759896,1419238266986, 5523689999096,21573875791838,84572021687714, 332542322089642,1309933674885610] |