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 | 87 |
| 4 | 547 |
| 5 | 3623 |
| 6 | 24885 |
| 7 | 175591 |
| 8 | 1265187 |
| 9 | 9271167 |
| 10 | 68894785 |
| 11 | 518053231 |
| 12 | 3935274277 |
| 13 | 30158804835 |
| 14 | 232930956175 |
| 15 | 1811476156847 |
| 16 | 14174669041427 |
| 17 | 111532445963367 |
| 18 | 882004732285473 |
| 19 | 7006931317108119 |
| 20 | 55899039962599777 |
| 21 | 447666261592033123 |