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 | 1 |
| 3 | 2 |
| 4 | 7 |
| 5 | 59 |
| 6 | 616 |
| 7 | 6992 |
| 8 | 90847 |
| 9 | 1352549 |
| 10 | 22591681 |
| 11 | 417527582 |
| 12 | 8465505412 |
| 13 | 186906393764 |
| 14 | 4463901355096 |
| 15 | 114672825810272 |
| 16 | 3153127461349327 |
| 17 | 92405864554182329 |
| 18 | 2875362251645606611 |
| 19 | 94680648376734042062 |
| 20 | 3289274269898822961967 |
| 21 | 120235993277078434540619 |