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 | 3 |
| 3 | 13 |
| 4 | 75 |
| 5 | 541 |
| 6 | 4683 |
| 7 | 47293 |
| 8 | 545835 |
| 9 | 7087260 |
| 10 | 102247543 |
| 11 | 1622632133 |
| 12 | 28091557915 |
| 13 | 526858128161 |
| 14 | 10641337741219 |
| 15 | 230283060907913 |
| 16 | 5315651289289195 |
| 17 | 130370674248854021 |
| 18 | 3385532005327322503 |
| 19 | 92801507648842580769 |
| 20 | 2677685300845992661475 |
| 21 | 81124743440296074264381 |