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 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 0 |
| 4 | 3 |
| 5 | 3 |
| 6 | 16 |
| 7 | 37 |
| 8 | 134 |
| 9 | 411 |
| 10 | 1411 |
| 11 | 4747 |
| 12 | 16500 |
| 13 | 57671 |
| 14 | 204380 |
| 15 | 730032 |
| 16 | 2629637 |
| 17 | 9535268 |
| 18 | 34787215 |
| 19 | 127585608 |
| 20 | 470162614 |
| 21 | 1739952061 |
| 22 | 6463845941 |
| 23 | 24096378885 |
| 24 | 90112499714 |
| 25 | 337965831635 |
| 26 | 1270901550454 |
| 27 | 4790836498608 |
| 28 | 18100497143361 |