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 | 3 |
| 5 | -3 |
| 6 | 11 |
| 7 | -47 |
| 8 | 291 |
| 9 | -361 |
| 10 | -327 |
| 11 | 2651 |
| 12 | 8117 |
| 13 | -23761 |
| 14 | -920509 |
| 15 | 3401813 |
| 16 | 48080231 |
| 17 | -949833905 |
| 18 | -533061737 |
| 19 | 47194458351 |
| 20 | 9309105461 |
| 21 | -5717668358773 |
| 22 | 5794759242411 |
| 23 | 416358013987311 |
| 24 | -3775846647202969 |
| 25 | -144292064358491357 |
| 26 | 269618719159718919 |
| 27 | 14658236743430975341 |