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 | -2 |
| 2 | 6 |
| 3 | -14 |
| 4 | 36 |
| 5 | -88 |
| 6 | 220 |
| 7 | -544 |
| 8 | 1352 |
| 9 | -3352 |
| 10 | 8320 |
| 11 | -20640 |
| 12 | 51216 |
| 13 | -127072 |
| 14 | 315296 |
| 15 | -782304 |
| 16 | 1941056 |
| 17 | -4816128 |
| 18 | 11949760 |
| 19 | -29649664 |
| 20 | 73566592 |
| 21 | -182532992 |
| 22 | 452899840 |
| 23 | -1123732480 |
| 24 | 2788198656 |
| 25 | -6918062592 |
| 26 | 17165057536 |
| 27 | -42589842944 |
| 28 | 105673675776 |
| 29 | -262196922368 |