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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 13 |
| 3 | 31 |
| 4 | 85 |
| 5 | 193 |
| 6 | 517 |
| 7 | 1165 |
| 8 | 3109 |
| 9 | 6997 |
| 10 | 18661 |
| 11 | 41989 |
| 12 | 111973 |
| 13 | 251941 |
| 14 | 671845 |
| 15 | 1511653 |
| 16 | 4031077 |
| 17 | 9069925 |
| 18 | 24186469 |
| 19 | 54419557 |
| 20 | 145118821 |
| 21 | 326517349 |
| 22 | 870712933 |
| 23 | 1959104101 |
| 24 | 5224277605 |
| 25 | 11754624613 |
| 26 | 31345665637 |
| 27 | 70527747685 |
[1,4,13,31,85,193,517,1165,3109,6997,18661,41989, 111973,251941,671845,1511653,4031077,9069925, 24186469,54419557,145118821,326517349,870712933, 1959104101,5224277605,11754624613,31345665637, 70527747685] |