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 | 1 |
| 3 | 20 |
| 4 | 448 |
| 5 | 13266 |
| 6 | 486744 |
| 7 | 21474640 |
| 8 | 1106532352 |
| 9 | 65221935740 |
| 10 | 4327576834420 |
| 11 | 319187489891256 |
| 12 | 25904823417117120 |
| 13 | 2294089575084464472 |
| 14 | 220132629092378694832 |
| 15 | 22751391952785312551232 |
| 16 | 2519687900505221042995200 |
| 17 | 297684761086121821704009432 |
| 18 | 37370623083548749203599933004 |