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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 6 |
| 6 | 25 |
| 7 | 91 |
| 8 | 311 |
| 9 | 1029 |
| 10 | 3346 |
| 11 | 10778 |
| 12 | 34544 |
| 13 | 110444 |
| 14 | 352785 |
| 15 | 1126885 |
| 16 | 3601617 |
| 17 | 11521648 |
| 18 | 36899528 |
| 19 | 118322448 |
| 20 | 379908707 |
| 21 | 1221423149 |
| 22 | 3932113059 |
| 23 | 12675055399 |
| 24 | 40909511880 |
| 25 | 132200481507 |
| 26 | 427718677728 |
| 27 | 1385419058692 |
| 28 | 4492446685542 |
| 29 | 14582927712740 |
| 30 | 47385785436719 |
[0,0,0,1,6,25,91,311,1029,3346,10778,34544,110444, 352785,1126885,3601617,11521648,36899528, 118322448,379908707,1221423149,3932113059, 12675055399,40909511880,132200481507,427718677728, 1385419058692,4492446685542,14582927712740, 47385785436719] |