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 | 0 |
| 1 | 3 |
| 2 | -6 |
| 3 | 33 |
| 4 | -288 |
| 5 | 3240 |
| 6 | -41328 |
| 7 | 538776 |
| 8 | -6772608 |
| 9 | 108502848 |
| 10 | -3985200000 |
| 11 | 160423053120 |
| 12 | -1094935449600 |
| 13 | -334098799856640 |
| 14 | 6171528273039360 |
| 15 | 2583214608931891200 |
| 16 | -150276838897808179200 |
| 17 | -27910708844766496358400 |
| 18 | 3428432556793417713254400 |
| 19 | 462153194693572097337753600 |
| 20 | -107869378361311784037187584000 |