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 | 1 |
| 2 | 7 |
| 3 | 50 |
| 4 | 386 |
| 5 | 3304 |
| 6 | 31176 |
| 7 | 323280 |
| 8 | 3656880 |
| 9 | 44890560 |
| 10 | 594463680 |
| 11 | 8453128320 |
| 12 | 128473430400 |
| 13 | 2079045964800 |
| 14 | 35692494566400 |
| 15 | 648044312832000 |
| 16 | 12406994498304000 |
| 17 | 249834635947008000 |
| 18 | 5278539223415808000 |
| 19 | 116768100285720576000 |
| 20 | 2699047267616544768000 |
| 21 | 65071515565786447872000 |