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 | 0 |
| 1 | 5 |
| 2 | 21 |
| 3 | 81 |
| 4 | 330 |
| 5 | 1287 |
| 6 | 4995 |
| 7 | 19448 |
| 8 | 75582 |
| 9 | 293895 |
| 10 | 1144066 |
| 11 | 4457400 |
| 12 | 17383734 |
| 13 | 67863915 |
| 14 | 265182525 |
| 15 | 1037157858 |
| 16 | 4059928950 |
| 17 | 15905368710 |
| 18 | 62359142274 |
| 19 | 244662670200 |
| 20 | 960566918220 |
| 21 | 3773655743715 |
| 22 | 14833897694226 |
| 23 | 58343356817424 |