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 | 4 |
| 3 | 20 |
| 4 | 127 |
| 5 | 977 |
| 6 | 8789 |
| 7 | 90267 |
| 8 | 1040260 |
| 9 | 13275258 |
| 10 | 185653535 |
| 11 | 2821321725 |
| 12 | 46265262553 |
| 13 | 813871304989 |
| 14 | 15281792484768 |
| 15 | 304949014412540 |
| 16 | 6442741397501699 |
| 17 | 143633948442619765 |
| 18 | 3369004776395733829 |
| 19 | 82919378806522132407 |
| 20 | 2136425765494805888952 |