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) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | -1 |
| 4 | -5 |
| 5 | 19 |
| 6 | -3 |
| 7 | -10187 |
| 8 | 146847 |
| 9 | 3268961 |
| 10 | -211632497 |
| 11 | 393324007 |
| 12 | 5402916117 |
| 13 | -3884618921299 |
| 14 | -774402304798329 |
| 15 | 148294948981707557 |
| 16 | -3311395903665985169 |
| 17 | -43463254022673425965 |
| 18 | 14469962812566878696039 |
| 19 | 6554498075974546253080309 |
| 20 | -3074689522272735111427973673 |