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 | 0 |
| 2 | 3 |
| 3 | 4 |
| 4 | 57 |
| 5 | 216 |
| 6 | 2755 |
| 7 | 18348 |
| 8 | 247569 |
| 9 | 2368432 |
| 10 | 35256771 |
| 11 | 436248660 |
| 12 | 7235178313 |
| 13 | 108919083144 |
| 14 | 2010150360387 |
| 15 | 35421547781116 |
| 16 | 723689454172065 |
| 17 | 14543895730321248 |
| 18 | 326843345169621379 |
| 19 | 7354350135365751972 |
| 20 | 180610925178770615001 |
| 21 | 4488323611011676811320 |