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 | 0 |
| 3 | -1 |
| 4 | 3 |
| 5 | 12 |
| 6 | -7 |
| 7 | -47 |
| 8 | 332 |
| 9 | 1347 |
| 10 | -2105 |
| 11 | -4200 |
| 12 | 135457 |
| 13 | 474697 |
| 14 | -900832 |
| 15 | 4682135 |
| 16 | 126196787 |
| 17 | 439488524 |
| 18 | 233313817 |
| 19 | 19129265609 |
| 20 | 239146712732 |
| 21 | 1104038984091 |
| 22 | 5891696027079 |
| 23 | 89831511761320 |
| 24 | 911995655018817 |
| 25 | 6253185308181553 |
| 26 | 54873149768926624 |
| 27 | 653039078246798383 |