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 | 3 |
| 3 | -24 |
| 4 | -240 |
| 5 | 1890 |
| 6 | 40446 |
| 7 | -311472 |
| 8 | -12038544 |
| 9 | 86898420 |
| 10 | 5614173180 |
| 11 | -36099955584 |
| 12 | -3786960576672 |
| 13 | 20307572439336 |
| 14 | 3492389655843480 |
| 15 | -14110473458954880 |
| 16 | -4223754447793582464 |
| 17 | 10493742733654512528 |
| 18 | 6488421280167604253616 |
| 19 | -4618066393756887442560 |
| 20 | -12344309538368967592151040 |