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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 0 |
| 3 | 4 |
| 4 | 14 |
| 5 | 72 |
| 6 | 370 |
| 7 | 1995 |
| 8 | 11064 |
| 9 | 62774 |
| 10 | 362614 |
| 11 | 2125479 |
| 12 | 12610410 |
| 13 | 75584363 |
| 14 | 457000668 |
| 15 | 2783991972 |
| 16 | 17071362986 |
| 17 | 105287143740 |
| 18 | 652687596388 |
| 19 | 4064618917998 |
| 20 | 25416557913498 |
| 21 | 159523021737403 |
| 22 | 1004594882114020 |
| 23 | 6345859437931884 |
| 24 | 40198433775513524 |
[0,1,0,4,14,72,370,1995,11064,62774,362614, 2125479,12610410,75584363,457000668,2783991972, 17071362986,105287143740,652687596388, 4064618917998,25416557913498,159523021737403, 1004594882114020,6345859437931884, 40198433775513524] |