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) |
|---|---|
| 2 | 2 |
| 3 | 28 |
| 4 | 252 |
| 5 | 1840 |
| 6 | 11924 |
| 7 | 71476 |
| 8 | 405204 |
| 9 | 2202724 |
| 10 | 11590162 |
| 11 | 59417180 |
| 12 | 298186524 |
| 13 | 1470151308 |
| 14 | 7140410208 |
| 15 | 34237750548 |
| 16 | 162350915772 |
| 17 | 762391407024 |
| 18 | 3549556185044 |
| 19 | 16400558514664 |
| 20 | 75263022053196 |