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) |
|---|---|
| 4 | 3 |
| 5 | 18 |
| 6 | 89 |
| 7 | 405 |
| 8 | 1701 |
| 9 | 6801 |
| 10 | 26244 |
| 11 | 98415 |
| 12 | 360846 |
| 13 | 1299078 |
| 14 | 4605822 |
| 15 | 16120350 |
| 16 | 55801305 |
| 17 | 191318760 |
| 18 | 650483703 |
| 19 | 2195382771 |
| 20 | 7360989291 |
| 21 | 24536630727 |
| 22 | 81358302690 |
| 23 | 268482398877 |
| 24 | 882156452724 |
| 25 | 2887057484028 |
| 26 | 9414317882700 |
| 27 | 30596533116588 |
| 28 | 99132767304831 |