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 | 3 |
| 2 | -6 |
| 3 | 30 |
| 4 | -159 |
| 5 | 939 |
| 6 | -5856 |
| 7 | 37992 |
| 8 | -253590 |
| 9 | 1729758 |
| 10 | -12001524 |
| 11 | 84422244 |
| 12 | -600613998 |
| 13 | 4313760870 |
| 14 | -31233564312 |
| 15 | 227721316008 |
| 16 | -1670358339735 |
| 17 | 12317389232475 |
| 18 | -91256834358510 |
| 19 | 678934503248070 |
| 20 | -5070123478493727 |
| 21 | 37990712430826059 |
| 22 | -285540106663543128 |