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 | 2 |
| 2 | -1 |
| 3 | 4 |
| 4 | -7 |
| 5 | 14 |
| 6 | -91 |
| 7 | 208 |
| 8 | -494 |
| 9 | 10868 |
| 10 | -27170 |
| 11 | 69160 |
| 12 | -535990 |
| 13 | 1401820 |
| 14 | -3704810 |
| 15 | 29638480 |
| 16 | -79653415 |
| 17 | 215532770 |
| 18 | -5280552865 |
| 19 | 14452039420 |
| 20 | -39743108405 |
| 21 | 329300041070 |
| 22 | -913059204785 |
| 23 | 2540686482880 |
| 24 | -21278249294120 |
| 25 | 59579098023536 |
| 26 | -167279775219928 |
| 27 | 12713262916714528 |