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 | 3 |
| 2 | 15 |
| 3 | 81 |
| 4 | 459 |
| 5 | 2673 |
| 6 | 15849 |
| 7 | 95175 |
| 8 | 576963 |
| 9 | 3523257 |
| 10 | 21640365 |
| 11 | 133549155 |
| 12 | 827418645 |
| 13 | 5143397535 |
| 14 | 32063180535 |
| 15 | 200367960201 |
| 16 | 1254816463923 |
| 17 | 7873205412825 |
| 18 | 49482344889261 |
| 19 | 311457546052659 |
| 20 | 1963051327342449 |
| 21 | 12387750763156227 |
| 22 | 78258731003169435 |