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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 13 |
| 4 | 73 |
| 5 | 501 |
| 6 | 4051 |
| 7 | 40153 |
| 8 | 434673 |
| 9 | 5231593 |
| 10 | 71641891 |
| 11 | 1051099941 |
| 12 | 16673401273 |
| 13 | 289579557853 |
| 14 | 5336892479283 |
| 15 | 104679769486321 |
| 16 | 2199654959898721 |
| 17 | 48682858073000913 |
| 18 | 1135029742772833603 |
| 19 | 27968526823231736893 |
| 20 | 721419709386600131241 |
[1,1,3,13,73,501,4051,40153,434673,5231593, 71641891,1051099941,16673401273,289579557853, 5336892479283,104679769486321,2199654959898721, 48682858073000913,1135029742772833603, 27968526823231736893,721419709386600131241] |