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 | 2 |
| 2 | 2 |
| 3 | 6 |
| 4 | 28 |
| 5 | 160 |
| 6 | 1036 |
| 7 | 7294 |
| 8 | 54548 |
| 9 | 426960 |
| 10 | 3463304 |
| 11 | 28910816 |
| 12 | 247104976 |
| 13 | 2154192248 |
| 14 | 19097610480 |
| 15 | 171769942086 |
| 16 | 1564484503044 |
| 17 | 14407366963440 |
| 18 | 133978878618904 |
| 19 | 1256799271555872 |
| 20 | 11881860129979440 |