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 | 0 |
| 2 | -1 |
| 3 | -3 |
| 4 | -4 |
| 5 | 15 |
| 6 | 149 |
| 7 | 672 |
| 8 | 1091 |
| 9 | -12855 |
| 10 | -162796 |
| 11 | -1060653 |
| 12 | -2925319 |
| 13 | 30881760 |
| 14 | 598929239 |
| 15 | 5688937797 |
| 16 | 29126981516 |
| 17 | -112222099065 |
| 18 | -4930674413971 |
| 19 | -69798552313728 |
| 20 | -598032658869829 |
| 21 | -1296500625378255 |
| 22 | 65193402297999524 |
| 23 | 1515140106814565547 |