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 | 1 |
| 3 | 0 |
| 4 | -2 |
| 5 | 2 |
| 6 | 9 |
| 7 | -24 |
| 8 | -80 |
| 9 | 339 |
| 10 | 1127 |
| 11 | -6438 |
| 12 | -22051 |
| 13 | 179670 |
| 14 | 705969 |
| 15 | -6316587 |
| 16 | -34059363 |
| 17 | 234694313 |
| 18 | 1788358694 |
| 19 | -10539103220 |
| 20 | -107105535812 |
| 21 | 679821765685 |
| 22 | 9404735956848 |
| 23 | -39383677719404 |
| 24 | -965379929608361 |
| 25 | 375758547940149 |
| 26 | 86199829280567638 |
| 27 | 158307964563289211 |