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 | 4 |
| 2 | 20 |
| 3 | 104 |
| 4 | 544 |
| 5 | 2848 |
| 6 | 14912 |
| 7 | 78080 |
| 8 | 408832 |
| 9 | 2140672 |
| 10 | 11208704 |
| 11 | 58689536 |
| 12 | 307302400 |
| 13 | 1609056256 |
| 14 | 8425127936 |
| 15 | 44114542592 |
| 16 | 230986743808 |
| 17 | 1209462292480 |
| 18 | 6332826779648 |
| 19 | 33159111507968 |
| 20 | 173623361929216 |
| 21 | 909103725543424 |
| 22 | 4760128905543680 |
| 23 | 24924358531088384 |
| 24 | 130505635564355584 |