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 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 10 |
| 5 | 28 |
| 6 | 84 |
| 7 | 264 |
| 8 | 860 |
| 9 | 2880 |
| 10 | 9862 |
| 11 | 34392 |
| 12 | 121770 |
| 13 | 436688 |
| 14 | 1583146 |
| 15 | 5793216 |
| 16 | 21370806 |
| 17 | 79391536 |
| 18 | 296760222 |
| 19 | 1115327844 |
| 20 | 4212125662 |
| 21 | 15976390684 |
| 22 | 60833679424 |
| 23 | 232452408632 |
| 24 | 891060970152 |
| 25 | 3425639505624 |
| 26 | 13204738280326 |
| 27 | 51024408662932 |
| 28 | 197607503526934 |