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 | 15 |
| 2 | 81 |
| 3 | 441 |
| 4 | 2151 |
| 5 | 9957 |
| 6 | 43122 |
| 7 | 174162 |
| 8 | 666267 |
| 9 | 2403987 |
| 10 | 8183601 |
| 11 | 26281065 |
| 12 | 79660856 |
| 13 | 228180456 |
| 14 | 618992466 |
| 15 | 1595081266 |
| 16 | 3918506466 |
| 17 | 9211519476 |
| 18 | 20797923546 |
| 19 | 45258309066 |
| 20 | 95225448306 |
| 21 | 194283668576 |
| 22 | 385361919996 |