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 | 2 |
| 2 | 6 |
| 3 | 18 |
| 4 | 66 |
| 5 | 214 |
| 6 | 666 |
| 7 | 2072 |
| 8 | 6306 |
| 9 | 19166 |
| 10 | 58020 |
| 11 | 175114 |
| 12 | 527358 |
| 13 | 1586122 |
| 14 | 4766560 |
| 15 | 14316138 |
| 16 | 42981210 |
| 17 | 129009096 |
| 18 | 387158352 |
| 19 | 1161737214 |
| 20 | 3485735826 |
| 21 | 10458256090 |
| 22 | 31376865294 |
| 23 | 94134790242 |
| 24 | 282412759224 |
| 25 | 847255054990 |
| 26 | 2541798719452 |
| 27 | 7625463267246 |
| 28 | 22876524019528 |
| 29 | 68629840494090 |
| 30 | 205890058352826 |