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 | 1 |
| 2 | 1 |
| 3 | -1 |
| 4 | -1 |
| 5 | 13 |
| 6 | -47 |
| 7 | -73 |
| 8 | 2447 |
| 9 | -16811 |
| 10 | -15551 |
| 11 | 1726511 |
| 12 | -18994849 |
| 13 | 10979677 |
| 14 | 2983409137 |
| 15 | -48421103257 |
| 16 | 135002366063 |
| 17 | 778870772857 |
| 18 | -232033147779359 |
| 19 | 1305952009204319 |
| 20 | 58740282660173759 |
| 21 | -1862057132555380307 |
| 22 | 16905219421196907793 |
| 23 | 527257187244811805207 |