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 | 0 |
| 2 | 1 |
| 3 | 9 |
| 4 | 65 |
| 5 | 421 |
| 6 | 2569 |
| 7 | 15085 |
| 8 | 86241 |
| 9 | 483429 |
| 10 | 2669305 |
| 11 | 14564061 |
| 12 | 78699089 |
| 13 | 421880725 |
| 14 | 2246459881 |
| 15 | 11894065549 |
| 16 | 62665617345 |
| 17 | 328756309701 |
| 18 | 1718275598809 |
| 19 | 8951067087165 |
| 20 | 46492068009521 |
| 21 | 240846026714869 |
| 22 | 1244719810538185 |
| 23 | 6419100507215341 |