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) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 15 |
| 5 | 97 |
| 6 | 767 |
| 7 | 7175 |
| 8 | 77497 |
| 9 | 949047 |
| 10 | 12993303 |
| 11 | 196655437 |
| 12 | 3260367539 |
| 13 | 58761008087 |
| 14 | 1143864229549 |
| 15 | 23917992791139 |
| 16 | 534642521054391 |
| 17 | 12722568903456817 |
| 18 | 321112383611040455 |
| 19 | 8568150193087139231 |
| 20 | 240986045600284560553 |
| 21 | 7125677277725450247087 |