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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 39 |
| 4 | 488 |
| 5 | 7615 |
| 6 | 147024 |
| 7 | 3371137 |
| 8 | 89079808 |
| 9 | 2665537713 |
| 10 | 89142430400 |
| 11 | 3295096700071 |
| 12 | 133399600068096 |
| 13 | 5870116973678191 |
| 14 | 278971698167158528 |
| 15 | 14239859507270510625 |
| 16 | 776985219329347518464 |
| 17 | 45130494178637796970273 |
| 18 | 2780224621391401396134912 |
| 19 | 181059775626543107582734183 |
[1,1,4,39,488,7615,147024,3371137,89079808, 2665537713,89142430400,3295096700071, 133399600068096,5870116973678191, 278971698167158528,14239859507270510625, 776985219329347518464,45130494178637796970273, 2780224621391401396134912, 181059775626543107582734183] |