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 | 5 |
| 3 | 21 |
| 4 | 94 |
| 5 | 485 |
| 6 | 2931 |
| 7 | 20545 |
| 8 | 164396 |
| 9 | 1479609 |
| 10 | 14796145 |
| 11 | 162757661 |
| 12 | 1953092010 |
| 13 | 25390196221 |
| 14 | 355462747199 |
| 15 | 5331941208105 |
| 16 | 85311059329816 |
| 17 | 1450288008607025 |
| 18 | 26105184154926621 |
| 19 | 495998498943605989 |
| 20 | 9919969978872119990 |