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 | 12 |
| 3 | 51 |
| 4 | 216 |
| 5 | 735 |
| 6 | 0 |
| 7 | -39081 |
| 8 | -575232 |
| 9 | -6047973 |
| 10 | -48314880 |
| 11 | -189159333 |
| 12 | 3046957056 |
| 13 | 99745485879 |
| 14 | 1789140627456 |
| 15 | 23433663134655 |
| 16 | 185580069027840 |
| 17 | -1250544374605389 |
| 18 | -94781673979379712 |
| 19 | -2543434372808424957 |
| 20 | -47763303489939701760 |
| 21 | -586864592847636893937 |