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 | 3 |
| 2 | 16 |
| 3 | 90 |
| 4 | 508 |
| 5 | 2868 |
| 6 | 16192 |
| 7 | 91416 |
| 8 | 516112 |
| 9 | 2913840 |
| 10 | 16450816 |
| 11 | 92877216 |
| 12 | 524361664 |
| 13 | 2960415552 |
| 14 | 16713769984 |
| 15 | 94361788800 |
| 16 | 532743192832 |
| 17 | 3007735579392 |
| 18 | 16980927090688 |
| 19 | 95870091385344 |
| 20 | 541258694130688 |