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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 42 |
| 3 | 696 |
| 4 | 4260 |
| 5 | 16680 |
| 6 | 50190 |
| 7 | 126672 |
| 8 | 281736 |
| 9 | 569520 |
| 10 | 1068210 |
| 11 | 1886280 |
| 12 | 3169452 |
| 13 | 5108376 |
| 14 | 7947030 |
| 15 | 11991840 |
| 16 | 17621520 |
| 17 | 25297632 |
| 18 | 35575866 |
| 19 | 49118040 |
| 20 | 66704820 |
| 21 | 89249160 |
| 22 | 117810462 |
| 23 | 153609456 |
| 24 | 198043800 |
| 25 | 252704400 |
| 26 | 319392450 |
| 27 | 400137192 |
[0,42,696,4260,16680,50190,126672,281736,569520, 1068210,1886280,3169452,5108376,7947030,11991840, 17621520,25297632,35575866,49118040,66704820, 89249160,117810462,153609456,198043800,252704400, 319392450,400137192] |