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 | 2 |
| 2 | 6 |
| 3 | 20 |
| 4 | 60 |
| 5 | 208 |
| 6 | 624 |
| 7 | 2080 |
| 8 | 6240 |
| 9 | 18720 |
| 10 | 58240 |
| 11 | 176000 |
| 12 | 529408 |
| 13 | 1593344 |
| 14 | 4780032 |
| 15 | 14344192 |
| 16 | 43040768 |
| 17 | 129138688 |
| 18 | 387416064 |
| 19 | 1162248192 |
| 20 | 3486777344 |
| 21 | 10460332032 |
| 22 | 31380996096 |
| 23 | 94142988288 |
| 24 | 282428964864 |
| 25 | 847286894592 |
| 26 | 2541860683776 |
| 27 | 7625582051328 |