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) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 18 |
| 3 | 85 |
| 4 | 410 |
| 5 | 1999 |
| 6 | 9807 |
| 7 | 48304 |
| 8 | 238570 |
| 9 | 1180615 |
| 10 | 5851253 |
| 11 | 29033074 |
| 12 | 144190943 |
| 13 | 716652070 |
| 14 | 3564079250 |
| 15 | 17734184365 |
| 16 | 88280673770 |
| 17 | 439625873215 |
| 18 | 2189988826125 |
| 19 | 10912480440850 |
| 20 | 54389237971285 |
| 21 | 271142650382080 |