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 | 7 |
| 3 | 21 |
| 4 | 75 |
| 5 | 213 |
| 6 | 699 |
| 7 | 1977 |
| 8 | 6351 |
| 9 | 19473 |
| 10 | 58839 |
| 11 | 174837 |
| 12 | 529131 |
| 13 | 1564293 |
| 14 | 4752939 |
| 15 | 14318877 |
| 16 | 43016691 |
| 17 | 128629653 |
| 18 | 386909979 |
| 19 | 1152561777 |
| 20 | 3477084711 |
| 21 | 10450653513 |
| 22 | 31371359919 |
| 23 | 93920085957 |
| 24 | 282206443611 |
| 25 | 847065516573 |
| 26 | 2541642735459 |
| 27 | 7625374392117 |
| 28 | 22876569362091 |