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 | 4 |
| 2 | 18 |
| 3 | 100 |
| 4 | 611 |
| 5 | 3964 |
| 6 | 26796 |
| 7 | 186664 |
| 8 | 1330541 |
| 9 | 9657748 |
| 10 | 71138964 |
| 11 | 530417668 |
| 12 | 3995461515 |
| 13 | 30359913132 |
| 14 | 232434013174 |
| 15 | 1791205897652 |
| 16 | 13883372595753 |
| 17 | 108159238126644 |
| 18 | 846472588860134 |
| 19 | 6651825146945508 |
| 20 | 52465622957295300 |
| 21 | 415208597109815172 |