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 | -1 |
| 3 | -4 |
| 4 | 7 |
| 5 | 33 |
| 6 | -68 |
| 7 | -344 |
| 8 | 767 |
| 9 | 4035 |
| 10 | -9425 |
| 11 | -50832 |
| 12 | 122436 |
| 13 | 671804 |
| 14 | -1653776 |
| 15 | -9189488 |
| 16 | 22992655 |
| 17 | 129001239 |
| 18 | -326863667 |
| 19 | -1847900500 |
| 20 | 4729547023 |
| 21 | 26903463697 |
| 22 | -69424933968 |
| 23 | -396930961632 |
| 24 | 1031309398852 |
| 25 | 5921685690388 |
| 26 | -15474833826028 |
| 27 | -89179284390112 |
| 28 | 234201961398776 |
| 29 | 1353916407418200 |