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 | 0 |
| 1 | 1 |
| 2 | 9 |
| 3 | 126 |
| 4 | 2028 |
| 5 | 35919 |
| 6 | 674964 |
| 7 | 13225632 |
| 8 | 267188229 |
| 9 | 5525568297 |
| 10 | 116400215521 |
| 11 | 2488984609644 |
| 12 | 53883301460607 |
| 13 | 1178671076752803 |
| 14 | 26011822261355487 |
| 15 | 578441979200964897 |
| 16 | 12948907700868521142 |
| 17 | 291569232606979152321 |
| 18 | 6599274332502483541080 |