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| n | a(n) |
|---|---|
| 1 | 40 |
| 2 | 180 |
| 3 | 808 |
| 4 | 3636 |
| 5 | 16396 |
| 6 | 74104 |
| 7 | 335660 |
| 8 | 1523420 |
| 9 | 6925768 |
| 10 | 31527492 |
| 11 | 143656108 |
| 12 | 654965928 |
| 13 | 2986993420 |
| 14 | 13622286844 |
| 15 | 62110476152 |
| 16 | 283072002980 |
| 17 | 1289383564204 |
| 18 | 5869109209272 |
| 19 | 26695147549612 |
| 20 | 121321864635996 |
| 21 | 550906942638568 |
[40,180,808,3636,16396,74104,335660,1523420, 6925768,31527492,143656108,654965928,2986993420, 13622286844,62110476152,283072002980, 1289383564204,5869109209272,26695147549612, 121321864635996,550906942638568] |