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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 7 |
| 3 | 21 |
| 4 | 83 |
| 5 | 287 |
| 6 | 1220 |
| 7 | 4555 |
| 8 | 20190 |
| 9 | 78993 |
| 10 | 359409 |
| 11 | 1451062 |
| 12 | 6720199 |
| 13 | 27751565 |
| 14 | 130164832 |
| 15 | 546754411 |
| 16 | 2588819975 |
| 17 | 11019871896 |
| 18 | 52557679338 |
| 19 | 226126679991 |
| 20 | 1084651213681 |
| 21 | 4707823016596 |
| 22 | 22685539977351 |
| 23 | 99191227846860 |
| 24 | 479765440775025 |
| 25 | 2110911015785133 |
| 26 | 10241763997702972 |
| 27 | 45306172200689549 |
[1,2,7,21,83,287,1220,4555,20190,78993,359409, 1451062,6720199,27751565,130164832,546754411, 2588819975,11019871896,52557679338,226126679991, 1084651213681,4707823016596,22685539977351, 99191227846860,479765440775025,2110911015785133, 10241763997702972,45306172200689549] |