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 | 1 |
| 2 | 3 |
| 3 | 9 |
| 4 | 33 |
| 5 | 201 |
| 6 | 1125 |
| 7 | 5259 |
| 8 | 98481 |
| 9 | 1176579 |
| 10 | 4970985 |
| 11 | 83471355 |
| 12 | 607500315 |
| 13 | 20298622815 |
| 14 | 302065005093 |
| 15 | 2979977447571 |
| 16 | 46728566085441 |
| 17 | 541457057096937 |
| 18 | 13094093041014057 |
| 19 | 231069516389617197 |
| 20 | 5992213273680818217 |