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 | 0 |
| 3 | 1 |
| 4 | 6 |
| 5 | 48 |
| 6 | 369 |
| 7 | 3341 |
| 8 | 33960 |
| 9 | 393467 |
| 10 | 5111052 |
| 11 | 73753685 |
| 12 | 1170468816 |
| 13 | 20263758984 |
| 14 | 380047813297 |
| 15 | 7676106093000 |
| 16 | 166114206886740 |
| 17 | 3834434320842720 |
| 18 | 94042629507381957 |
| 19 | 2442147034668044933 |
| 20 | 66942194905675830162 |
| 21 | 1931543452344523775050 |
| 22 | 58519191359155952404837 |