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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 25 |
| 4 | 200 |
| 5 | 1888 |
| 6 | 20158 |
| 7 | 237357 |
| 8 | 3032188 |
| 9 | 41554144 |
| 10 | 605964370 |
| 11 | 9345693140 |
| 12 | 151727166822 |
| 13 | 2583300560490 |
| 14 | 45984983349166 |
| 15 | 853637181574329 |
| 16 | 16489023127843088 |
| 17 | 330789284905928356 |
| 18 | 6880312907650893934 |
| 19 | 148151276593976715612 |
| 20 | 3297947033016039111690 |
[1,1,4,25,200,1888,20158,237357,3032188,41554144, 605964370,9345693140,151727166822,2583300560490, 45984983349166,853637181574329,16489023127843088, 330789284905928356,6880312907650893934, 148151276593976715612,3297947033016039111690] |