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 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 18 |
| 5 | 60 |
| 6 | 204 |
| 7 | 734 |
| 8 | 2694 |
| 9 | 10162 |
| 10 | 38982 |
| 11 | 151920 |
| 12 | 599244 |
| 13 | 2389028 |
| 14 | 9608668 |
| 15 | 38945230 |
| 16 | 158904230 |
| 17 | 652178206 |
| 18 | 2690598570 |
| 19 | 11151718166 |
| 20 | 46412717826 |
| 21 | 193891596436 |
| 22 | 812748036380 |
| 23 | 3417407089470 |
| 24 | 14410094628558 |
| 25 | 60920843101858 |
| 26 | 258169745573158 |
| 27 | 1096494947168142 |