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 | 11 |
| 5 | 45 |
| 6 | 197 |
| 7 | 901 |
| 8 | 4259 |
| 9 | 20643 |
| 10 | 102035 |
| 11 | 512365 |
| 12 | 2606421 |
| 13 | 13403715 |
| 14 | 69568071 |
| 15 | 363946211 |
| 16 | 1917148173 |
| 17 | 10160087333 |
| 18 | 54132552109 |
| 19 | 289790960735 |
| 20 | 1557980372127 |
| 21 | 8408281616305 |
| 22 | 45536927325809 |
| 23 | 247397689058521 |