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 | 1 |
| 3 | 4 |
| 4 | 13 |
| 5 | 96 |
| 6 | 541 |
| 7 | 5888 |
| 8 | 47545 |
| 9 | 686080 |
| 10 | 7231801 |
| 11 | 130179072 |
| 12 | 1695106117 |
| 13 | 36590059520 |
| 14 | 567547087381 |
| 15 | 14290429935616 |
| 16 | 257320926233329 |
| 17 | 7405376630685696 |
| 18 | 151856004814953841 |
| 19 | 4917457306800619520 |
| 20 | 113144789723082206461 |
| 21 | 4071967909087792857088 |