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) |
|---|---|
| 3 | 6 |
| 4 | 42 |
| 5 | 252 |
| 6 | 1620 |
| 7 | 11730 |
| 8 | 95886 |
| 9 | 876792 |
| 10 | 8877672 |
| 11 | 98640990 |
| 12 | 1193556210 |
| 13 | 15624736116 |
| 14 | 220048367292 |
| 15 | 3317652307242 |
| 16 | 53319412081110 |
| 17 | 909984632851440 |
| 18 | 16436597430879696 |
| 19 | 313262209859119542 |
| 20 | 6282647653285675962 |