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) |
|---|---|
| 2 | 1 |
| 3 | 3 |
| 4 | 15 |
| 5 | 85 |
| 6 | 531 |
| 7 | 3600 |
| 8 | 26266 |
| 9 | 205353 |
| 10 | 1716582 |
| 11 | 15321056 |
| 12 | 145819266 |
| 13 | 1477589301 |
| 14 | 15908557455 |
| 15 | 181553715486 |
| 16 | 2190398368254 |
| 17 | 27859946518796 |
| 18 | 372542199781464 |
| 19 | 5223365137285467 |
| 20 | 76597458027515272 |
| 21 | 1172078722366916586 |