This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 21 |
| 4 | 181 |
| 5 | 1746 |
| 6 | 18039 |
| 7 | 195214 |
| 8 | 2184381 |
| 9 | 25067856 |
| 10 | 293420578 |
| 11 | 3489516381 |
| 12 | 42044519283 |
| 13 | 512146618088 |
| 14 | 6296546349018 |
| 15 | 78031090301868 |
| 16 | 973723814391957 |
| 17 | 12224652295383324 |
| 18 | 154299365902579044 |
| 19 | 1956876044969421604 |
| 20 | 24924046596321581940 |