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 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 1 |
| 7 | 1 |
| 8 | 1 |
| 9 | 2 |
| 10 | 5 |
| 11 | 15 |
| 12 | 64 |
| 13 | 342 |
| 14 | 2344 |
| 15 | 19090 |
| 16 | 179562 |
| 17 | 1878277 |
| 18 | 21365403 |
| 19 | 258965451 |
| 20 | 3294561195 |
| 21 | 43472906719 |
| 22 | 589744428065 |
| 23 | 8171396893523 |
| 24 | 115094557122380 |
| 25 | 1642269376265063 |
| 26 | 23679803216530017 |
| 27 | 344396036645439675 |
| 28 | 5045351124912000756 |