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 | 7 |
| 2 | 42 |
| 3 | 252 |
| 4 | 1512 |
| 5 | 9072 |
| 6 | 54411 |
| 7 | 326340 |
| 8 | 1957305 |
| 9 | 11739420 |
| 10 | 70410060 |
| 11 | 422301600 |
| 12 | 2532857460 |
| 13 | 15191434125 |
| 14 | 91114353750 |
| 15 | 546480693675 |
| 16 | 3277652052150 |
| 17 | 19658522431800 |
| 18 | 117906811965600 |
| 19 | 707175035973000 |
| 20 | 4241455800274875 |