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 | 0 |
| 3 | 1 |
| 4 | 1 |
| 5 | 3 |
| 6 | 13 |
| 7 | 24 |
| 8 | 67 |
| 9 | 252 |
| 10 | 1795 |
| 11 | 4038 |
| 12 | 16812 |
| 13 | 61750 |
| 14 | 349806 |
| 15 | 3485026 |
| 16 | 10391070 |
| 17 | 49433135 |
| 18 | 240064988 |
| 19 | 1282012986 |
| 20 | 9167581934 |
| 21 | 131550811985 |
| 22 | 459677212302 |
| 23 | 2707382738558 |
| 24 | 14318807586215 |
| 25 | 94084166753923 |
| 26 | 601900541189696 |
| 27 | 5894253303715121 |