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 | 1 |
| 2 | 3 |
| 3 | 12 |
| 4 | 60 |
| 5 | 358 |
| 6 | 2471 |
| 7 | 19302 |
| 8 | 167894 |
| 9 | 1606137 |
| 10 | 16733779 |
| 11 | 188378402 |
| 12 | 2276423485 |
| 13 | 29367807524 |
| 14 | 402577243425 |
| 15 | 5840190914957 |
| 16 | 89345001017415 |
| 17 | 1436904211547895 |
| 18 | 24227076487779802 |
| 19 | 427187837301557598 |
| 20 | 7859930038606521508 |
| 21 | 150601795280158255827 |