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 | 1 |
| 3 | -1 |
| 4 | 0 |
| 5 | 4 |
| 6 | -5 |
| 7 | 13 |
| 8 | -392 |
| 9 | 2112 |
| 10 | 7663 |
| 11 | -165067 |
| 12 | 1011560 |
| 13 | -2965756 |
| 14 | -11164309 |
| 15 | 630876517 |
| 16 | -12760548400 |
| 17 | 133046910432 |
| 18 | -189966787521 |
| 19 | -18567623055795 |
| 20 | 392188656574896 |
| 21 | -5061972266268844 |
| 22 | 33655544331988203 |
| 23 | 565132153437469165 |
| 24 | -26647451471277927416 |