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 | 7 |
| 2 | 42 |
| 3 | 252 |
| 4 | 1722 |
| 5 | 11802 |
| 6 | 82362 |
| 7 | 574812 |
| 8 | 4021962 |
| 9 | 28141932 |
| 10 | 196981722 |
| 11 | 1378789692 |
| 12 | 9651445482 |
| 13 | 67559543562 |
| 14 | 472916230122 |
| 15 | 3310409588892 |
| 16 | 23172863100282 |
| 17 | 162210013560042 |
| 18 | 1135470066778362 |
| 19 | 7948290270466812 |
| 20 | 55638031696285962 |
| 21 | 389466220495212042 |