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 | 0 |
| 3 | 1 |
| 4 | 4 |
| 5 | 19 |
| 6 | 112 |
| 7 | 771 |
| 8 | 6088 |
| 9 | 54213 |
| 10 | 537392 |
| 11 | 5867925 |
| 12 | 69975308 |
| 13 | 904788263 |
| 14 | 12607819040 |
| 15 | 188341689287 |
| 16 | 3002539594128 |
| 17 | 50878366664393 |
| 18 | 913161208490016 |
| 19 | 17304836525709097 |
| 20 | 345279674107957524 |
| 21 | 7235298537356113339 |