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 | 0 |
| 2 | 1 |
| 3 | 4 |
| 4 | 34 |
| 5 | 260 |
| 6 | 2275 |
| 7 | 21784 |
| 8 | 228676 |
| 9 | 2614296 |
| 10 | 32372805 |
| 11 | 431971100 |
| 12 | 6182204006 |
| 13 | 94495208444 |
| 14 | 1536740258599 |
| 15 | 26498747241680 |
| 16 | 482990781797000 |
| 17 | 9279452377499504 |
| 18 | 187442757190618761 |
| 19 | 3971627425918503156 |
| 20 | 88084356619901450410 |
| 21 | 2040857112777615061300 |