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 | -3 |
| 2 | 6 |
| 3 | -21 |
| 4 | 69 |
| 5 | -201 |
| 6 | 591 |
| 7 | -1785 |
| 8 | 5406 |
| 9 | -16194 |
| 10 | 48426 |
| 11 | -145380 |
| 12 | 436641 |
| 13 | -1309611 |
| 14 | 3927399 |
| 15 | -11783280 |
| 16 | 35354139 |
| 17 | -106059387 |
| 18 | 318165729 |
| 19 | -954506190 |
| 20 | 2863556475 |
| 21 | -8590643832 |
| 22 | 25771817454 |
| 23 | -77315531169 |
| 24 | 231946940175 |
| 25 | -695840583126 |
| 26 | 2087520715788 |
| 27 | -6262562872614 |