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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 33 |
| 4 | 195 |
| 5 | 1763 |
| 6 | 15623 |
| 7 | 156257 |
| 8 | 1630947 |
| 9 | 17911299 |
| 10 | 203739015 |
| 11 | 2389928995 |
| 12 | 28749060871 |
| 13 | 353362388551 |
| 14 | 4424242664975 |
| 15 | 56290517376737 |
| 16 | 726355164976547 |
| 17 | 9490129871680355 |
| 18 | 125375330053632455 |
| 19 | 1672895457018337859 |
| 20 | 22522481793315373319 |
| 21 | 305695116823973096519 |
[1,1,3,33,195,1763,15623,156257,1630947,17911299, 203739015,2389928995,28749060871,353362388551, 4424242664975,56290517376737,726355164976547, 9490129871680355,125375330053632455, 1672895457018337859,22522481793315373319, 305695116823973096519] |