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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 5 |
| 4 | 18 |
| 5 | 141 |
| 6 | 602 |
| 7 | 2180 |
| 8 | 7006 |
| 9 | 20979 |
| 10 | 59698 |
| 11 | 163635 |
| 12 | 435900 |
| 13 | 1135036 |
| 14 | 2901852 |
| 15 | 7307093 |
| 16 | 18167506 |
| 17 | 44683929 |
| 18 | 108886702 |
| 19 | 263208036 |
| 20 | 631773802 |
| 21 | 1507041943 |
| 22 | 3575151970 |
| 23 | 8439694735 |
| 24 | 19835439712 |
| 25 | 46433224508 |
| 26 | 108305733064 |
| 27 | 251797970649 |
[0,0,5,18,141,602,2180,7006,20979,59698,163635, 435900,1135036,2901852,7307093,18167506,44683929, 108886702,263208036,631773802,1507041943, 3575151970,8439694735,19835439712,46433224508, 108305733064,251797970649] |