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 | 4 |
| 3 | -20 |
| 4 | 78 |
| 5 | -282 |
| 6 | 1048 |
| 7 | -4014 |
| 8 | 15456 |
| 9 | -59224 |
| 10 | 227646 |
| 11 | -879694 |
| 12 | 3407730 |
| 13 | -13219372 |
| 14 | 51375286 |
| 15 | -200021556 |
| 16 | 779870542 |
| 17 | -3044448644 |
| 18 | 11898709560 |
| 19 | -46553635346 |
| 20 | 182315752476 |
| 21 | -714619687038 |
| 22 | 2803342734160 |
| 23 | -11005274516610 |
| 24 | 43233909672938 |
| 25 | -169951684067602 |
| 26 | 668474115081988 |