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 | 140 |
| 5 | 1089 |
| 6 | 8796 |
| 7 | 72204 |
| 8 | 596906 |
| 9 | 4958736 |
| 10 | 41365110 |
| 11 | 346477770 |
| 12 | 2914165157 |
| 13 | 24612003577 |
| 14 | 208711039484 |
| 15 | 1776879432103 |
| 16 | 15185140895506 |
| 17 | 130242884479498 |
| 18 | 1120949733518971 |
| 19 | 9679158242220797 |
| 20 | 83836374509942511 |
| 21 | 728279201686023394 |
| 22 | 6344019713842496995 |