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 | 3 |
| 2 | 15 |
| 3 | 99 |
| 4 | 807 |
| 5 | 7803 |
| 6 | 87135 |
| 7 | 1102419 |
| 8 | 15575127 |
| 9 | 242943723 |
| 10 | 4145495055 |
| 11 | 76797289539 |
| 12 | 1534762643847 |
| 13 | 32907617073243 |
| 14 | 753473367606975 |
| 15 | 18347287182129459 |
| 16 | 473409784213526967 |
| 17 | 12902366605394652363 |
| 18 | 370357953441110390895 |
| 19 | 11167936445234485414179 |