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 | 4033 |
| 3 | 530713 |
| 4 | 16773121 |
| 5 | 244125001 |
| 6 | 2176735681 |
| 7 | 13841169553 |
| 8 | 68719214593 |
| 9 | 282429005041 |
| 10 | 999999000001 |
| 11 | 3138426605161 |
| 12 | 8916097462273 |
| 13 | 23298080295673 |
| 14 | 56693904845761 |
| 15 | 129746326500001 |
| 16 | 281474959933441 |
| 17 | 582622213092193 |
| 18 | 1156831347413953 |
| 19 | 2213314872020281 |
| 20 | 4095999936000001 |