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 | 1 |
| 2 | 3 |
| 3 | 12 |
| 4 | 84 |
| 5 | 924 |
| 6 | 16632 |
| 7 | 482328 |
| 8 | 22669416 |
| 9 | 1722875616 |
| 10 | 211913700768 |
| 11 | 42170826452832 |
| 12 | 13579006117811904 |
| 13 | 7074662187380001984 |
| 14 | 5963940223961341672512 |
| 15 | 8134814465483270041306368 |
| 16 | 17953535525321576981163154176 |
| 17 | 64112075360923351399733623562496 |
| 18 | 370439571435415124387660876944101888 |