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 | 0 |
| 1 | -1 |
| 2 | 58 |
| 3 | -180 |
| 4 | -1304 |
| 5 | -2920 |
| 6 | 1008 |
| 7 | 34496 |
| 8 | 163840 |
| 9 | 525312 |
| 10 | 1285120 |
| 11 | 2241536 |
| 12 | 1124352 |
| 13 | -12113920 |
| 14 | -72052736 |
| 15 | -282378240 |
| 16 | -924581888 |
| 17 | -2699493376 |
| 18 | -7201751040 |
| 19 | -17666670592 |
| 20 | -39507722240 |
| 21 | -77918109696 |
| 22 | -121883328512 |
| 23 | -78622228480 |
| 24 | 453588811776 |
| 25 | 2904974950400 |
| 26 | 11885785120768 |