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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 12 |
| 4 | 51 |
| 5 | 190 |
| 6 | 802 |
| 7 | 3356 |
| 8 | 14562 |
| 9 | 64178 |
| 10 | 285563 |
| 11 | 1289048 |
| 12 | 5867405 |
| 13 | 26897377 |
| 14 | 124355469 |
| 15 | 577261044 |
| 16 | 2696986274 |
| 17 | 12649353895 |
| 18 | 59567612679 |
| 19 | 281586404327 |
| 20 | 1334914705198 |
| 21 | 6348129828108 |
| 22 | 30264057313283 |
| 23 | 144617531435220 |
| 24 | 692610958926307 |
| 25 | 3323350481472771 |
| 26 | 15976197017662252 |
| 27 | 76929032013370252 |
[1,1,4,12,51,190,802,3356,14562,64178,285563, 1289048,5867405,26897377,124355469,577261044, 2696986274,12649353895,59567612679,281586404327, 1334914705198,6348129828108,30264057313283, 144617531435220,692610958926307,3323350481472771, 15976197017662252,76929032013370252] |