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 | 2 |
| 3 | 6 |
| 4 | 23 |
| 5 | 105 |
| 6 | 549 |
| 7 | 3207 |
| 8 | 20577 |
| 9 | 143239 |
| 10 | 1071704 |
| 11 | 8555388 |
| 12 | 72442465 |
| 13 | 647479819 |
| 14 | 6083742438 |
| 15 | 59885558106 |
| 16 | 615718710929 |
| 17 | 6595077685263 |
| 18 | 73424063891526 |
| 19 | 847916751131054 |
| 20 | 10138485386085013 |
| 21 | 125310003360265231 |