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 | 4682 |
| 7 | 47278 |
| 8 | 545594 |
| 9 | 7083258 |
| 10 | 102177222 |
| 11 | 1621316466 |
| 12 | 28065324210 |
| 13 | 526301293518 |
| 14 | 10628781887724 |
| 15 | 229983021824556 |
| 16 | 5308071700475544 |
| 17 | 130168746864660504 |
| 18 | 3379871981604782664 |
| 19 | 92634950510491052664 |
| 20 | 2672550322299614660904 |