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 | 2 |
| 1 | 6 |
| 2 | 40 |
| 3 | 350 |
| 4 | 3528 |
| 5 | 38808 |
| 6 | 453024 |
| 7 | 5521230 |
| 8 | 69526600 |
| 9 | 898283672 |
| 10 | 11848435872 |
| 11 | 158966514616 |
| 12 | 2163449607200 |
| 13 | 29802622140000 |
| 14 | 414852500188800 |
| 15 | 5827381213589550 |
| 16 | 82510878636707400 |
| 17 | 1176544010190087000 |
| 18 | 16882265852589060000 |
| 19 | 243611096252860135800 |