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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 13 |
| 4 | 49 |
| 5 | 186 |
| 6 | 751 |
| 7 | 3098 |
| 8 | 13036 |
| 9 | 55559 |
| 10 | 239741 |
| 11 | 1045683 |
| 12 | 4598980 |
| 13 | 20368516 |
| 14 | 90733028 |
| 15 | 406321477 |
| 16 | 1827966938 |
| 17 | 8257125139 |
| 18 | 37430455001 |
| 19 | 170216663711 |
| 20 | 776294282712 |
| 21 | 3549614438904 |
| 22 | 16269011949135 |
| 23 | 74726516665971 |
| 24 | 343909812071896 |
| 25 | 1585633519847133 |
| 26 | 7323006530686385 |
| 27 | 33872716318708966 |
[1,1,4,13,49,186,751,3098,13036,55559,239741, 1045683,4598980,20368516,90733028,406321477, 1827966938,8257125139,37430455001,170216663711, 776294282712,3549614438904,16269011949135, 74726516665971,343909812071896,1585633519847133, 7323006530686385,33872716318708966] |