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 | 25 |
| 4 | -251 |
| 5 | 2817 |
| 6 | -33843 |
| 7 | 425769 |
| 8 | -5537835 |
| 9 | 73865617 |
| 10 | -1004862179 |
| 11 | 13888533561 |
| 12 | -194475377243 |
| 13 | 2752994728225 |
| 14 | -39333541106835 |
| 15 | 566464908534345 |
| 16 | -8214515461250955 |
| 17 | 119845125957958065 |
| 18 | -1757855400878129475 |
| 19 | 25906894146115000665 |
| 20 | -383443906519878272955 |