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 | -3 |
| 4 | 0 |
| 5 | 5 |
| 6 | -2 |
| 7 | -6 |
| 8 | 18 |
| 9 | -28 |
| 10 | -9 |
| 11 | 232 |
| 12 | -949 |
| 13 | 2147 |
| 14 | 579 |
| 15 | -34487 |
| 16 | 202078 |
| 17 | -680541 |
| 18 | 527630 |
| 19 | 11789818 |
| 20 | -104485820 |
| 21 | 520965294 |
| 22 | -1270746269 |
| 23 | -5790611092 |
| 24 | 98629011681 |
| 25 | -729706466727 |
| 26 | 3269817273787 |
| 27 | -2007499839343 |
| 28 | -131143854669640 |
| 29 | 1558206734632453 |