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 | 0 |
| 3 | 3 |
| 4 | 4 |
| 5 | 65 |
| 6 | 726 |
| 7 | 8617 |
| 8 | 127688 |
| 9 | 2374353 |
| 10 | 50692330 |
| 11 | 1198835561 |
| 12 | 31297606572 |
| 13 | 901114484569 |
| 14 | 28449258421598 |
| 15 | 976863784939785 |
| 16 | 36199494609008656 |
| 17 | 1438734246518372897 |
| 18 | 61037354387458904274 |
| 19 | 2753490065023053584713 |
| 20 | 131645635680595606832180 |