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 | 23 |
| 3 | 148 |
| 4 | 977 |
| 5 | 6484 |
| 6 | 43079 |
| 7 | 286276 |
| 8 | 1902497 |
| 9 | 12643492 |
| 10 | 84025463 |
| 11 | 558412276 |
| 12 | 3711069041 |
| 13 | 24662841844 |
| 14 | 163903113383 |
| 15 | 1089259330468 |
| 16 | 7238946623297 |
| 17 | 48108239012164 |
| 18 | 319715392487639 |
| 19 | 2124748988791636 |
| 20 | 14120553377944337 |