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Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 4 |
| 6 | 20 |
| 7 | 121 |
| 8 | 862 |
| 9 | 7000 |
| 10 | 63876 |
| 11 | 646743 |
| 12 | 7195013 |
| 13 | 87239530 |
| 14 | 1145018832 |
| 15 | 16173391002 |
| 16 | 244622538903 |
| 17 | 3944538439806 |
| 18 | 67550220781672 |
| 19 | 1224347751667801 |
| 20 | 23415650750646696 |
| 21 | 471239971356764754 |
[1,0,0,0,1,4,20,121,862,7000,63876,646743,7195013, 87239530,1145018832,16173391002,244622538903, 3944538439806,67550220781672,1224347751667801, 23415650750646696,471239971356764754] |