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) |
|---|---|
| 3 | 1 |
| 4 | 6 |
| 5 | -25 |
| 6 | -135 |
| 7 | 1834 |
| 8 | -3668 |
| 9 | -110692 |
| 10 | 1339020 |
| 11 | -1181664 |
| 12 | -164709864 |
| 13 | 2206092096 |
| 14 | 395662176 |
| 15 | -463716547776 |
| 16 | 7029335571840 |
| 17 | 8900411569920 |
| 18 | -2265668505227520 |
| 19 | 38689597829053440 |
| 20 | 92447263589921280 |
| 21 | -17785648201625856000 |
| 22 | 338957966532455424000 |