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 | 9 |
| 2 | 57 |
| 3 | 312 |
| 4 | 1578 |
| 5 | 7599 |
| 6 | 35401 |
| 7 | 161052 |
| 8 | 719790 |
| 9 | 3173090 |
| 10 | 13836426 |
| 11 | 59803104 |
| 12 | 256596276 |
| 13 | 1094249019 |
| 14 | 4642178601 |
| 15 | 19605872724 |
| 16 | 82483419846 |
| 17 | 345839048094 |
| 18 | 1445715336366 |
| 19 | 6027524015664 |
| 20 | 25070662980876 |
| 21 | 104056307673654 |