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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 12 |
| 5 | 30 |
| 6 | 90 |
| 7 | 210 |
| 8 | 560 |
| 9 | 1680 |
| 10 | 4200 |
| 11 | 11550 |
| 12 | 34650 |
| 13 | 90090 |
| 14 | 252252 |
| 15 | 756756 |
| 16 | 2018016 |
| 17 | 5717712 |
| 18 | 17153136 |
| 19 | 46558512 |
| 20 | 133024320 |
| 21 | 399072960 |
| 22 | 1097450640 |
| 23 | 3155170590 |
| 24 | 9465511770 |
| 25 | 26293088250 |
| 26 | 75957810500 |
| 27 | 227873431500 |
| 28 | 638045608200 |
| 29 | 1850332263780 |
| 30 | 5550996791340 |
[1,1,2,6,12,30,90,210,560,1680,4200,11550,34650, 90090,252252,756756,2018016,5717712,17153136, 46558512,133024320,399072960,1097450640, 3155170590,9465511770,26293088250,75957810500, 227873431500,638045608200,1850332263780, 5550996791340] |