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 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | -7 |
| 4 | 32 |
| 5 | -120 |
| 6 | 401 |
| 7 | -1247 |
| 8 | 3712 |
| 9 | -10800 |
| 10 | 31201 |
| 11 | -90487 |
| 12 | 264992 |
| 13 | -784680 |
| 14 | 2345201 |
| 15 | -7051727 |
| 16 | 21263872 |
| 17 | -64145760 |
| 18 | 193310401 |
| 19 | -581652967 |
| 20 | 1747480352 |
| 21 | -5243918040 |
| 22 | 15725054801 |
| 23 | -47140982207 |
| 24 | 141319714432 |
| 25 | -423717125520 |
| 26 | 1270699466401 |
| 27 | -3811500847447 |
| 28 | 11434371886112 |
| 29 | -34305580792200 |
| 30 | 102927256193201 |
| 31 | -308811498176687 |