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 | 15 |
| 2 | 117 |
| 3 | 891 |
| 4 | 6777 |
| 5 | 51543 |
| 6 | 392013 |
| 7 | 2981475 |
| 8 | 22675761 |
| 9 | 172461663 |
| 10 | 1311666021 |
| 11 | 9975943179 |
| 12 | 75872547369 |
| 13 | 577052549415 |
| 14 | 4388802753213 |
| 15 | 33379264377459 |
| 16 | 253867706760033 |
| 17 | 1930803860947887 |
| 18 | 14684827767302997 |
| 19 | 111686210555580315 |
| 20 | 849435201142733529 |
| 21 | 6460422977475127287 |