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 | 9 |
| 4 | 31 |
| 5 | 109 |
| 6 | 421 |
| 7 | 1585 |
| 8 | 5454 |
| 9 | 20681 |
| 10 | 80983 |
| 11 | 311221 |
| 12 | 1168531 |
| 13 | 4505761 |
| 14 | 17907735 |
| 15 | 69240865 |
| 16 | 272109736 |
| 17 | 1078430833 |
| 18 | 4147985381 |
| 19 | 16383884581 |
| 20 | 64335012378 |
| 21 | 234179431201 |
| 22 | 929947274509 |
| 23 | 3651532869601 |
| 24 | 14453209093051 |
| 25 | 56596999501225 |