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 | 8 |
| 3 | 24 |
| 4 | 72 |
| 5 | 222 |
| 6 | 688 |
| 7 | 2128 |
| 8 | 6576 |
| 9 | 20322 |
| 10 | 62808 |
| 11 | 194120 |
| 12 | 599960 |
| 13 | 1854270 |
| 14 | 5730912 |
| 15 | 17712288 |
| 16 | 54742624 |
| 17 | 169190722 |
| 18 | 522910632 |
| 19 | 1616137848 |
| 20 | 4994929128 |
| 21 | 15437616926 |
| 22 | 47712391952 |
| 23 | 147462678768 |
| 24 | 455756685840 |
| 25 | 1408587979170 |
| 26 | 4353463496440 |
| 27 | 13455066133672 |