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 | 1 |
| 3 | 3 |
| 4 | 7 |
| 5 | 21 |
| 6 | 75 |
| 7 | 256 |
| 8 | 929 |
| 9 | 3090 |
| 10 | 9235 |
| 11 | 21216 |
| 12 | 80463 |
| 13 | 138623 |
| 14 | 423595 |
| 15 | 1160355 |
| 16 | 2456117 |
| 17 | 4272856 |
| 18 | 15986299 |
| 19 | 21709209 |
| 20 | 75452662 |
| 21 | 156068738 |