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 | 0 |
| 1 | 1 |
| 2 | 5 |
| 3 | 21 |
| 4 | 89 |
| 5 | 393 |
| 6 | 1805 |
| 7 | 8557 |
| 8 | 41585 |
| 9 | 206097 |
| 10 | 1037717 |
| 11 | 5293445 |
| 12 | 27297737 |
| 13 | 142078745 |
| 14 | 745387037 |
| 15 | 3937603037 |
| 16 | 20927156705 |
| 17 | 111818026017 |
| 18 | 600318853925 |
| 19 | 3236724317173 |