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 | 9 |
| 4 | 31 |
| 5 | 129 |
| 6 | 651 |
| 7 | 3913 |
| 8 | 27399 |
| 9 | 219201 |
| 10 | 1972819 |
| 11 | 19728201 |
| 12 | 217010223 |
| 13 | 2604122689 |
| 14 | 33853594971 |
| 15 | 473950329609 |
| 16 | 7109254944151 |
| 17 | 113748079106433 |
| 18 | 1933717344809379 |
| 19 | 34806912206568841 |
| 20 | 661331331924807999 |
| 21 | 13226626638496160001 |
| 22 | 277759159408419360043 |