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 | 2 |
| 2 | -8 |
| 3 | 60 |
| 4 | -552 |
| 5 | 5648 |
| 6 | -61712 |
| 7 | 705104 |
| 8 | -8321696 |
| 9 | 100658368 |
| 10 | -1241281536 |
| 11 | 15546987648 |
| 12 | -197234640384 |
| 13 | 2529169695232 |
| 14 | -32728878054144 |
| 15 | 426864306146560 |
| 16 | -5605439340018176 |
| 17 | 74050470138645504 |
| 18 | -983432207024885760 |
| 19 | 13122261492710033408 |
| 20 | -175836387068096147456 |