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) |
|---|---|
| 1 | 4 |
| 2 | 20 |
| 3 | 52 |
| 4 | 240 |
| 5 | 984 |
| 6 | 4412 |
| 7 | 20252 |
| 8 | 91808 |
| 9 | 406748 |
| 10 | 1759740 |
| 11 | 7455484 |
| 12 | 31056840 |
| 13 | 127719296 |
| 14 | 520368940 |
| 15 | 2106440916 |
| 16 | 8489650480 |
| 17 | 34118389900 |
| 18 | 136865613068 |
| 19 | 548408972596 |
| 20 | 2195889958776 |
| 21 | 8788865312160 |
| 22 | 35167823753468 |
| 23 | 140699850287804 |