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 | 12 |
| 2 | 90 |
| 3 | 560 |
| 4 | 3150 |
| 5 | 16632 |
| 6 | 84084 |
| 7 | 411840 |
| 8 | 1969110 |
| 9 | 9237800 |
| 10 | 42678636 |
| 11 | 194699232 |
| 12 | 878850700 |
| 13 | 3931426800 |
| 14 | 17450721000 |
| 15 | 76938289920 |
| 16 | 337206098790 |
| 17 | 1470171918600 |
| 18 | 6379820115900 |
| 19 | 27569305764000 |
| 20 | 118685861314020 |
| 21 | 509191949220240 |
| 22 | 2177742427450200 |
| 23 | 9287309860732800 |