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 | 0 |
| 2 | 5 |
| 3 | 10 |
| 4 | 65 |
| 5 | 260 |
| 6 | 1365 |
| 7 | 6510 |
| 8 | 32865 |
| 9 | 162760 |
| 10 | 815365 |
| 11 | 4069010 |
| 12 | 20352865 |
| 13 | 101725260 |
| 14 | 508665365 |
| 15 | 2543131510 |
| 16 | 12715852865 |
| 17 | 63578287760 |
| 18 | 317892415365 |
| 19 | 1589457194010 |
| 20 | 7947290852865 |
| 21 | 39736429850260 |