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 | 3 |
| 3 | -4 |
| 4 | 25 |
| 5 | 24 |
| 6 | 721 |
| 7 | 5942 |
| 8 | 82209 |
| 9 | 1186280 |
| 10 | 19956241 |
| 11 | 373942194 |
| 12 | 7768988833 |
| 13 | 177018731876 |
| 14 | 4389959146665 |
| 15 | 117700102748654 |
| 16 | 3392361669670081 |
| 17 | 104592876707106672 |
| 18 | 3434908281762030049 |
| 19 | 119702402508549928490 |
| 20 | 4411764405039931048641 |