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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 40 |
| 3 | 612 |
| 4 | 11976 |
| 5 | 276836 |
| 6 | 7336248 |
| 7 | 219610532 |
| 8 | 7331824360 |
| 9 | 269576919908 |
| 10 | 10796426089880 |
| 11 | 466904884431268 |
| 12 | 21658080409800264 |
| 13 | 1071807203930733668 |
| 14 | 56328256034260866296 |
| 15 | 3131089417758323092388 |
[1,4,40,612,11976,276836,7336248,219610532, 7331824360,269576919908,10796426089880, 466904884431268,21658080409800264, 1071807203930733668,56328256034260866296, 3131089417758323092388] |