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 | -4 |
| 3 | -1 |
| 4 | 21 |
| 5 | 29 |
| 6 | -80 |
| 7 | -244 |
| 8 | 153 |
| 9 | 1473 |
| 10 | 836 |
| 11 | -6920 |
| 12 | -12220 |
| 13 | 23209 |
| 14 | 91213 |
| 15 | -21511 |
| 16 | -510680 |
| 17 | -457965 |
| 18 | 2210520 |
| 19 | 4921941 |
| 20 | -6271749 |
| 21 | -33288595 |
| 22 | -3876765 |
| 23 | 173223185 |
| 24 | 214943855 |
| 25 | -682969376 |
| 26 | -1912499375 |
| 27 | 1498348275 |
| 28 | 11882164650 |
| 29 | 5332839025 |
| 30 | -57402248250 |
| 31 | -92821609874 |