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 | 0 |
| 1 | 1 |
| 2 | 5 |
| 3 | 31 |
| 4 | 247 |
| 5 | 5891 |
| 6 | 175669 |
| 7 | 6639823 |
| 8 | 290694979 |
| 9 | 13885515383 |
| 10 | 746406329689 |
| 11 | 44593096214321 |
| 12 | 3020489689357037 |
| 13 | 222690147603898211 |
| 14 | 17752712881208877899 |
| 15 | 1486130275559909484787 |
| 16 | 133315968357656471537153 |
| 17 | 13025132201814060676912631 |
| 18 | 2913672358303309675918969343 |
| 19 | 663425761972477930761347977351 |
| 20 | 152383524508438692136746106396609 |