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) |
|---|---|
| 1 | 3 |
| 2 | 24 |
| 3 | 140 |
| 4 | 1028 |
| 5 | 7791 |
| 6 | 66027 |
| 7 | 508368 |
| 8 | 4293464 |
| 9 | 33177954 |
| 10 | 282310785 |
| 11 | 2226471492 |
| 12 | 18845872240 |
| 13 | 149352193586 |
| 14 | 1252800269866 |
| 15 | 9919439949887 |
| 16 | 82782378005253 |
| 17 | 656171911832714 |
| 18 | 5446960364973500 |
| 19 | 43213785216715427 |
| 20 | 357463895275500826 |