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 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 17 |
| 5 | 80 |
| 6 | 468 |
| 7 | 3197 |
| 8 | 25042 |
| 9 | 221209 |
| 10 | 2175217 |
| 11 | 23564850 |
| 12 | 278850730 |
| 13 | 3578584369 |
| 14 | 49503750432 |
| 15 | 734305631413 |
| 16 | 11626505830701 |
| 17 | 195712848150141 |
| 18 | 3490212458677514 |
| 19 | 65732334638426516 |
| 20 | 1303691303662125906 |