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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 6 |
| 3 | 36 |
| 4 | 282 |
| 5 | 2575 |
| 6 | 28075 |
| 7 | 340809 |
| 8 | 4657996 |
| 9 | 69874305 |
| 10 | 1145441713 |
| 11 | 20279904337 |
| 12 | 386803154474 |
| 13 | 7874727448757 |
| 14 | 170678885319787 |
| 15 | 3919163707551187 |
| 16 | 95029714996046680 |
| 17 | 2424604353738271201 |
| 18 | 64940619086990938317 |
| 19 | 1820746123923294245293 |
| 20 | 53328181409328560026038 |
[1,1,6,36,282,2575,28075,340809,4657996,69874305, 1145441713,20279904337,386803154474,7874727448757, 170678885319787,3919163707551187, 95029714996046680,2424604353738271201, 64940619086990938317,1820746123923294245293, 53328181409328560026038] |