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 | 20 |
| 4 | 135 |
| 5 | 770 |
| 6 | 4004 |
| 7 | 19656 |
| 8 | 92820 |
| 9 | 426360 |
| 10 | 1918620 |
| 11 | 8498776 |
| 12 | 37182145 |
| 13 | 161056350 |
| 14 | 691945800 |
| 15 | 2952675600 |
| 16 | 12527780760 |
| 17 | 52895074320 |
| 18 | 222399744300 |
| 19 | 931689977400 |
| 20 | 3890668331550 |
| 21 | 16201562020644 |
| 22 | 67298796085752 |
| 23 | 278927990831600 |
| 24 | 1153747598439800 |
| 25 | 4763749454427600 |
| 26 | 19637233862140440 |