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 | 3 |
| 1 | 15 |
| 2 | 93 |
| 3 | 645 |
| 4 | 4737 |
| 5 | 35925 |
| 6 | 277833 |
| 7 | 2175405 |
| 8 | 17168097 |
| 9 | 136171365 |
| 10 | 1083508473 |
| 11 | 8638764765 |
| 12 | 68963621457 |
| 13 | 550976525205 |
| 14 | 4404150043113 |
| 15 | 35214889699725 |
| 16 | 281627564666817 |
| 17 | 2252562753269445 |
| 18 | 18018213207009753 |
| 19 | 144134261562708285 |