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 | 15 |
| 3 | 159 |
| 4 | 867 |
| 5 | 19239 |
| 6 | 107985 |
| 7 | 1222563 |
| 8 | 6965835 |
| 9 | 319153335 |
| 10 | 1835486085 |
| 11 | 21185534577 |
| 12 | 122622340677 |
| 13 | 2846090375067 |
| 14 | 16550504577861 |
| 15 | 192854402926251 |
| 16 | 1125503935556763 |
| 17 | 105252693980913879 |
| 18 | 615999836125850637 |
| 19 | 7219077361263238917 |
| 20 | 42347454581722163361 |
| 21 | 994637701798929524937 |