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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 25 |
| 4 | 208 |
| 5 | 2161 |
| 6 | 26944 |
| 7 | 391945 |
| 8 | 6515968 |
| 9 | 121866721 |
| 10 | 2532496384 |
| 11 | 57890223865 |
| 12 | 1443611004928 |
| 13 | 38999338931281 |
| 14 | 1134616226381824 |
| 15 | 35367467110007785 |
| 16 | 1175946733416153088 |
| 17 | 41543231955279099841 |
| 18 | 1553948045857778827264 |
| 19 | 61355543097139813855705 |
[1,1,4,25,208,2161,26944,391945,6515968,121866721, 2532496384,57890223865,1443611004928, 38999338931281,1134616226381824,35367467110007785, 1175946733416153088,41543231955279099841, 1553948045857778827264,61355543097139813855705] |