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 | 0 |
| 2 | 20 |
| 3 | 68 |
| 4 | 400 |
| 5 | 1940 |
| 6 | 9982 |
| 7 | 50400 |
| 8 | 256018 |
| 9 | 1297924 |
| 10 | 6584320 |
| 11 | 33394958 |
| 12 | 169387004 |
| 13 | 859152000 |
| 14 | 4357755890 |
| 15 | 22103183110 |
| 16 | 112110699524 |
| 17 | 568642349004 |
| 18 | 2884239836106 |
| 19 | 14629299498936 |
| 20 | 74202014273586 |
| 21 | 376363810775194 |