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 | 1 |
| 2 | 15 |
| 3 | 175 |
| 4 | 1827 |
| 5 | 17791 |
| 6 | 164955 |
| 7 | 1475335 |
| 8 | 12844707 |
| 9 | 109581871 |
| 10 | 920591595 |
| 11 | 7643833495 |
| 12 | 62904774387 |
| 13 | 514168732351 |
| 14 | 4180996130235 |
| 15 | 33864296127655 |
| 16 | 273465115692867 |
| 17 | 2203291473841231 |
| 18 | 17721094011796875 |
| 19 | 142344054436901815 |