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) |
|---|---|
| 1 | 1 |
| 2 | -1 |
| 3 | 6 |
| 4 | -8 |
| 5 | 20 |
| 6 | -30 |
| 7 | 70 |
| 8 | -136 |
| 9 | 270 |
| 10 | -500 |
| 11 | 1034 |
| 12 | -2088 |
| 13 | 4108 |
| 14 | -8134 |
| 15 | 16440 |
| 16 | -32912 |
| 17 | 65552 |
| 18 | -130878 |
| 19 | 262162 |
| 20 | -524800 |
| 21 | 1048740 |
| 22 | -2096138 |
| 23 | 4194326 |
| 24 | -8390976 |
| 25 | 16777300 |
| 26 | -33550348 |
| 27 | 67109418 |
| 28 | -134225840 |
| 29 | 268435484 |
| 30 | -536855640 |
| 31 | 1073741854 |
| 32 | -2147516704 |
| 33 | 4294969404 |