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 | -1 |
| 2 | 2 |
| 3 | -4 |
| 4 | 9 |
| 5 | -22 |
| 6 | 54 |
| 7 | -139 |
| 8 | 372 |
| 9 | -948 |
| 10 | 2607 |
| 11 | -7388 |
| 12 | 16058 |
| 13 | -58957 |
| 14 | 174854 |
| 15 | 210448 |
| 16 | 4345025 |
| 17 | -2008714 |
| 18 | -165872030 |
| 19 | -1756557123 |
| 20 | -6144936528 |
| 21 | 60244093040 |
| 22 | 1164910003567 |
| 23 | 8228177887688 |
| 24 | -10562519450714 |
| 25 | -967088274083133 |
| 26 | -11322641425582454 |
| 27 | -37483806372774364 |