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) |
|---|---|
| 1 | 9 |
| 2 | 15 |
| 3 | 39 |
| 4 | 124 |
| 5 | 405 |
| 6 | 1344 |
| 7 | 4548 |
| 8 | 15765 |
| 9 | 55763 |
| 10 | 199928 |
| 11 | 723468 |
| 12 | 2637378 |
| 13 | 9677509 |
| 14 | 35714337 |
| 15 | 132445734 |
| 16 | 493209254 |
| 17 | 1843263534 |
| 18 | 6910868397 |