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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 5 |
| 3 | 20 |
| 4 | 101 |
| 5 | 525 |
| 6 | 2887 |
| 7 | 16359 |
| 8 | 95115 |
| 9 | 563838 |
| 10 | 3395642 |
| 11 | 20716254 |
| 12 | 127764434 |
| 13 | 795256210 |
| 14 | 4989327246 |
| 15 | 31518412352 |
| 16 | 200311909083 |
| 17 | 1279869928686 |
| 18 | 8216519744870 |
| 19 | 52973522292775 |
| 20 | 342843762187861 |
| 21 | 2226606216608385 |
| 22 | 14506570969312335 |
| 23 | 94785565057725600 |
[1,1,5,20,101,525,2887,16359,95115,563838,3395642, 20716254,127764434,795256210,4989327246, 31518412352,200311909083,1279869928686, 8216519744870,52973522292775,342843762187861, 2226606216608385,14506570969312335, 94785565057725600] |