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 | 4 |
| 2 | 16 |
| 3 | 60 |
| 4 | 220 |
| 5 | 788 |
| 6 | 2780 |
| 7 | 9684 |
| 8 | 33404 |
| 9 | 114292 |
| 10 | 388444 |
| 11 | 1312788 |
| 12 | 4415548 |
| 13 | 14790836 |
| 14 | 49369628 |
| 15 | 164279892 |
| 16 | 545170172 |
| 17 | 1804855540 |
| 18 | 5962578652 |
| 19 | 19661140116 |
| 20 | 64722276796 |
| 21 | 212738159924 |
| 22 | 698312564636 |
| 23 | 2289419181780 |
| 24 | 7497612860540 |