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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 21 |
| 4 | 149 |
| 5 | 1317 |
| 6 | 13985 |
| 7 | 173207 |
| 8 | 2451807 |
| 9 | 39043963 |
| 10 | 690844441 |
| 11 | 13446183857 |
| 12 | 285500221447 |
| 13 | 6567135007015 |
| 14 | 162678487750465 |
| 15 | 4317650962178897 |
| 16 | 122234460353464081 |
| 17 | 3676789159574231397 |
| 18 | 117102826395968235853 |
| 19 | 3936834192059910096205 |
| 20 | 139316727760914366716635 |
[1,1,4,21,149,1317,13985,173207,2451807,39043963, 690844441,13446183857,285500221447,6567135007015, 162678487750465,4317650962178897, 122234460353464081,3676789159574231397, 117102826395968235853,3936834192059910096205, 139316727760914366716635] |