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 | 3 |
| 1 | 7 |
| 2 | 18 |
| 3 | 56 |
| 4 | 126 |
| 5 | 434 |
| 6 | 1332 |
| 7 | 3836 |
| 8 | 10476 |
| 9 | 42560 |
| 10 | 109926 |
| 11 | 315112 |
| 12 | 816732 |
| 13 | 2790074 |
| 14 | 8906760 |
| 15 | 30220288 |
| 16 | 64570086 |
| 17 | 229156928 |
| 18 | 706911048 |
| 19 | 2034690952 |
| 20 | 5357742012 |
| 21 | 21838961760 |
| 22 | 56496274632 |
| 23 | 164750562956 |
| 24 | 456919958880 |
| 25 | 1517043139136 |
| 26 | 4661686010664 |
| 27 | 16489453890560 |