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 | 3 |
| 2 | -18 |
| 3 | 180 |
| 4 | -2187 |
| 5 | 29484 |
| 6 | -424116 |
| 7 | 6377292 |
| 8 | -99034650 |
| 9 | 1576075644 |
| 10 | -25569752274 |
| 11 | 421325812440 |
| 12 | -7031733125508 |
| 13 | 118620405322020 |
| 14 | -2019349799669160 |
| 15 | 34647126360607440 |
| 16 | -598525520999144643 |
| 17 | 10401492640172342940 |
| 18 | -181721630178565389900 |
| 19 | 3189811189331825319492 |