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 | 1 |
| 5 | -5 |
| 6 | 27 |
| 7 | -9 |
| 8 | 171 |
| 9 | -69 |
| 10 | -579 |
| 11 | 10689 |
| 12 | -60261 |
| 13 | 116535 |
| 14 | -304555 |
| 15 | 268707 |
| 16 | 7942071 |
| 17 | -19570935 |
| 18 | 9537731 |
| 19 | 1117836325 |
| 20 | -630737297 |
| 21 | -52310180977 |
| 22 | 618435378229 |
| 23 | 523526983623 |
| 24 | -3672122551119 |
| 25 | 8661572895987 |
| 26 | 1205887924659627 |
| 27 | -8604836834766111 |
| 28 | -77855893119175779 |