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 | 2 |
| 3 | 4 |
| 4 | 6 |
| 5 | -1 |
| 6 | -58 |
| 7 | -304 |
| 8 | -1090 |
| 9 | -2876 |
| 10 | -4216 |
| 11 | 9244 |
| 12 | 106746 |
| 13 | 529962 |
| 14 | 1874628 |
| 15 | 4669760 |
| 16 | 4309742 |
| 17 | -35179252 |
| 18 | -277928680 |
| 19 | -1269921008 |
| 20 | -4214431912 |
| 21 | -9197175241 |
| 22 | 30113526 |
| 23 | 128659598896 |
| 24 | 822227670866 |
| 25 | 3453484223084 |
| 26 | 10519017940952 |
| 27 | 18490932535144 |