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) |
|---|---|
| 2 | 1 |
| 3 | 1 |
| 4 | 3 |
| 5 | 7 |
| 6 | 20 |
| 7 | 55 |
| 8 | 162 |
| 9 | 477 |
| 10 | 1450 |
| 11 | 4446 |
| 12 | 13858 |
| 13 | 43589 |
| 14 | 138515 |
| 15 | 443487 |
| 16 | 1430261 |
| 17 | 4640312 |
| 18 | 15137893 |
| 19 | 49620637 |
| 20 | 163360133 |
| 21 | 539904503 |
| 22 | 1790699059 |
| 23 | 5958280016 |
| 24 | 19883532941 |
| 25 | 66532519727 |
| 26 | 223177199775 |
| 27 | 750340752081 |
| 28 | 2528058240115 |