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 | 2 |
| 3 | 3 |
| 4 | -4 |
| 5 | -35 |
| 6 | -18 |
| 7 | 679 |
| 8 | 2200 |
| 9 | -18567 |
| 10 | -150150 |
| 11 | 587499 |
| 12 | 11618004 |
| 13 | -9780459 |
| 14 | -1078005082 |
| 15 | -2502478065 |
| 16 | 118928710576 |
| 17 | 742659420913 |
| 18 | -15184771406478 |
| 19 | -178572619407021 |
| 20 | 2148536703814700 |
| 21 | 44455465546363725 |