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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 21 |
| 5 | 81 |
| 6 | 330 |
| 7 | 1378 |
| 8 | 5931 |
| 9 | 26103 |
| 10 | 116949 |
| 11 | 531180 |
| 12 | 2439942 |
| 13 | 11308763 |
| 14 | 52813717 |
| 15 | 248226279 |
| 16 | 1173038179 |
| 17 | 5569350953 |
| 18 | 26549412251 |
| 19 | 127009530189 |
| 20 | 609483954875 |
| 21 | 2932752862535 |
| 22 | 14146308968347 |
| 23 | 68383627370230 |
| 24 | 331211588348031 |
| 25 | 1607013923709855 |
| 26 | 7809477167061254 |
| 27 | 38005744065563414 |
[1,1,2,6,21,81,330,1378,5931,26103,116949,531180, 2439942,11308763,52813717,248226279,1173038179, 5569350953,26549412251,127009530189,609483954875, 2932752862535,14146308968347,68383627370230, 331211588348031,1607013923709855,7809477167061254, 38005744065563414] |