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 | 12 |
| 3 | 41 |
| 4 | 159 |
| 5 | 685 |
| 6 | 3233 |
| 7 | 16534 |
| 8 | 90862 |
| 9 | 532958 |
| 10 | 3317613 |
| 11 | 21803646 |
| 12 | 150528288 |
| 13 | 1086089333 |
| 14 | 8146481406 |
| 15 | 63182485967 |
| 16 | 504037166445 |
| 17 | 4115582321241 |
| 18 | 34244236336515 |
| 19 | 289252828167957 |
| 20 | 2472398717507023 |
| 21 | 21329556857593204 |