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 | 3 |
| 2 | 15 |
| 3 | 57 |
| 4 | 195 |
| 5 | 633 |
| 6 | 1995 |
| 7 | 6177 |
| 8 | 18915 |
| 9 | 57513 |
| 10 | 174075 |
| 11 | 525297 |
| 12 | 1582035 |
| 13 | 4758393 |
| 14 | 14299755 |
| 15 | 42948417 |
| 16 | 128943555 |
| 17 | 387027273 |
| 18 | 1161475035 |
| 19 | 3485211537 |
| 20 | 10457207475 |
| 21 | 31374768153 |
| 22 | 94130595915 |
| 23 | 282404370657 |
| 24 | 847238277795 |
| 25 | 2541765165033 |
| 26 | 7625396158395 |
| 27 | 22876389801777 |
| 28 | 68629572058515 |