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 | 2 |
| 3 | 6 |
| 4 | 20 |
| 5 | 84 |
| 6 | 412 |
| 7 | 2300 |
| 8 | 14676 |
| 9 | 104536 |
| 10 | 825660 |
| 11 | 7168860 |
| 12 | 67826340 |
| 13 | 695174208 |
| 14 | 7671602644 |
| 15 | 90700227700 |
| 16 | 1143825611348 |
| 17 | 15325929083336 |
| 18 | 217429459642252 |
| 19 | 3256039887793868 |
| 20 | 51325896829151684 |
| 21 | 849518895902379696 |
| 22 | 14730333827970237220 |
| 23 | 267028337196612514596 |
| 24 | 5051094767395355339476 |