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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 5 |
| 2 | 20 |
| 3 | 105 |
| 4 | 520 |
| 5 | 2580 |
| 6 | 12945 |
| 7 | 64680 |
| 8 | 323320 |
| 9 | 1616780 |
| 10 | 8083745 |
| 11 | 40418380 |
| 12 | 202092620 |
| 13 | 1010462480 |
| 14 | 5052310420 |
| 15 | 25261556205 |
| 16 | 126307777920 |
| 17 | 631538879180 |
| 18 | 3157694416720 |
| 19 | 15788472066780 |
| 20 | 78942360284720 |
| 21 | 394711801527505 |
| 22 | 1973559007551520 |
| 23 | 9867795037511480 |
| 24 | 49338975188073020 |
[1,5,20,105,520,2580,12945,64680,323320,1616780, 8083745,40418380,202092620,1010462480,5052310420, 25261556205,126307777920,631538879180, 3157694416720,15788472066780,78942360284720, 394711801527505,1973559007551520,9867795037511480, 49338975188073020] |