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 | 1 |
| 2 | 3 |
| 3 | 20 |
| 4 | 152 |
| 5 | 1264 |
| 6 | 11168 |
| 7 | 102976 |
| 8 | 979840 |
| 9 | 9550592 |
| 10 | 94876160 |
| 11 | 957101056 |
| 12 | 9778354176 |
| 13 | 100970557440 |
| 14 | 1052097552384 |
| 15 | 11048512143360 |
| 16 | 116814955118592 |
| 17 | 1242454765535232 |
| 18 | 13284730164346880 |
| 19 | 142713773337346048 |
| 20 | 1539605733158944768 |