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 | 3 |
| 3 | 7 |
| 4 | 19 |
| 5 | 53 |
| 6 | 153 |
| 7 | 451 |
| 8 | 1339 |
| 9 | 4001 |
| 10 | 11981 |
| 11 | 35919 |
| 12 | 107727 |
| 13 | 323149 |
| 14 | 969409 |
| 15 | 2908187 |
| 16 | 8724515 |
| 17 | 26173497 |
| 18 | 78520437 |
| 19 | 235561255 |
| 20 | 706683703 |