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 | 1 |
| 1 | 0 |
| 2 | 4 |
| 3 | 12 |
| 4 | 52 |
| 5 | 204 |
| 6 | 820 |
| 7 | 3276 |
| 8 | 13108 |
| 9 | 52428 |
| 10 | 209716 |
| 11 | 838860 |
| 12 | 3355444 |
| 13 | 13421772 |
| 14 | 53687092 |
| 15 | 214748364 |
| 16 | 858993460 |
| 17 | 3435973836 |
| 18 | 13743895348 |
| 19 | 54975581388 |
| 20 | 219902325556 |
| 21 | 879609302220 |
| 22 | 3518437208884 |
| 23 | 14073748835532 |