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 | 60 |
| 3 | 240 |
| 4 | 912 |
| 5 | 3312 |
| 6 | 11664 |
| 7 | 40176 |
| 8 | 136080 |
| 9 | 454896 |
| 10 | 1504656 |
| 11 | 4933872 |
| 12 | 16061328 |
| 13 | 51963120 |
| 14 | 167226768 |
| 15 | 535692528 |
| 16 | 1709114256 |
| 17 | 5433452784 |
| 18 | 17218688400 |
| 19 | 54411055344 |
| 20 | 171498136464 |
| 21 | 539289320688 |
| 22 | 1692252695952 |
| 23 | 5299912289520 |