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 | -4 |
| 2 | 4 |
| 3 | -4 |
| 4 | 20 |
| 5 | -36 |
| 6 | 52 |
| 7 | -116 |
| 8 | 244 |
| 9 | -500 |
| 10 | 964 |
| 11 | -1876 |
| 12 | 3876 |
| 13 | -7780 |
| 14 | 15332 |
| 15 | -30628 |
| 16 | 61684 |
| 17 | -123460 |
| 18 | 246036 |
| 19 | -491988 |
| 20 | 985492 |
| 21 | -1971284 |
| 22 | 3939556 |
| 23 | -7878068 |
| 24 | 15762692 |
| 25 | -31527428 |
| 26 | 63041220 |
| 27 | -126078916 |
| 28 | 252185044 |
| 29 | -504375460 |
| 30 | 1008698036 |
| 31 | -2017385268 |
| 32 | 4034873268 |