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) |
|---|---|
| 1 | 1 |
| 2 | -1 |
| 3 | 1 |
| 4 | -2 |
| 5 | 11 |
| 6 | -3 |
| 7 | -11 |
| 8 | 29 |
| 9 | 493 |
| 10 | -2711 |
| 11 | -12406 |
| 12 | 2636317 |
| 13 | -10597579 |
| 14 | -439018457 |
| 15 | 1165403153 |
| 16 | 118734633647 |
| 17 | -105428488301 |
| 18 | -4070802683898 |
| 19 | 1695077946695371 |
| 20 | 56532812889378221 |
| 21 | -252968859037883917 |
| 22 | -425882179787933647571 |
| 23 | 123624959518930226565553 |
| 24 | 32729394708071881944913 |
| 25 | -5814212300444136523052695 |