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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 3 |
| 5 | 20 |
| 6 | 130 |
| 7 | 924 |
| 8 | 7413 |
| 9 | 66744 |
| 10 | 667476 |
| 11 | 7342280 |
| 12 | 88107415 |
| 13 | 1145396460 |
| 14 | 16035550518 |
| 15 | 240533257860 |
| 16 | 3848532125865 |
| 17 | 65425046139824 |
| 18 | 1177650830516968 |
| 19 | 22375365779822544 |
| 20 | 447507315596451051 |
| 21 | 9397653627525472260 |
| 22 | 206748379805560389930 |
| 23 | 4755212735527888968620 |
[1,0,0,0,3,20,130,924,7413,66744,667476,7342280, 88107415,1145396460,16035550518,240533257860, 3848532125865,65425046139824,1177650830516968, 22375365779822544,447507315596451051, 9397653627525472260,206748379805560389930, 4755212735527888968620] |