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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 13 |
| 3 | 47 |
| 4 | 202 |
| 5 | 982 |
| 6 | 5119 |
| 7 | 27819 |
| 8 | 155545 |
| 9 | 888517 |
| 10 | 5162089 |
| 11 | 30406466 |
| 12 | 181164254 |
| 13 | 1089858766 |
| 14 | 6610791274 |
| 15 | 40386823863 |
| 16 | 248278003097 |
| 17 | 1534716252481 |
| 18 | 9533278498468 |
| 19 | 59477997359141 |
| 20 | 372545818015840 |
| 21 | 2341796524294495 |
| 22 | 14768075460084253 |
[1,4,13,47,202,982,5119,27819,155545,888517, 5162089,30406466,181164254,1089858766,6610791274, 40386823863,248278003097,1534716252481, 9533278498468,59477997359141,372545818015840, 2341796524294495,14768075460084253] |