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 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | -1 |
| 6 | -15 |
| 7 | -140 |
| 8 | -1050 |
| 9 | -6951 |
| 10 | -42399 |
| 11 | -239800 |
| 12 | -1164570 |
| 13 | -2553551 |
| 14 | 54771717 |
| 15 | 1384600854 |
| 16 | 23301803070 |
| 17 | 340911045929 |
| 18 | 4600861076433 |
| 19 | 58236569430172 |
| 20 | 687816515641206 |
| 21 | 7315220762286129 |
| 22 | 61629305427537309 |
| 23 | 140107851269900954 |
| 24 | -11001310744922517426 |