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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 40 |
| 3 | 367 |
| 4 | 4745 |
| 5 | 68379 |
| 6 | 1072086 |
| 7 | 16821330 |
| 8 | 254092124 |
| 9 | 3608247685 |
| 10 | 47733362102 |
| 11 | 587016912645 |
| 12 | 6721970343643 |
| 13 | 71907225898320 |
| 14 | 721352899257954 |
| 15 | 6812732993272120 |
| 16 | 60802368520799533 |
| 17 | 514586622373193034 |
| 18 | 4143078743506122930 |
| 19 | 31825800605751740274 |
[1,4,40,367,4745,68379,1072086,16821330,254092124, 3608247685,47733362102,587016912645,6721970343643, 71907225898320,721352899257954,6812732993272120, 60802368520799533,514586622373193034, 4143078743506122930,31825800605751740274] |