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 | 0 |
| 2 | 1 |
| 3 | 4 |
| 4 | 12 |
| 5 | 36 |
| 6 | 100 |
| 7 | 288 |
| 8 | 805 |
| 9 | 2288 |
| 10 | 6471 |
| 11 | 18420 |
| 12 | 52426 |
| 13 | 149832 |
| 14 | 428649 |
| 15 | 1229354 |
| 16 | 3530715 |
| 17 | 10157552 |
| 18 | 29259703 |
| 19 | 84396168 |
| 20 | 243698332 |
| 21 | 704436640 |
| 22 | 2038158801 |
| 23 | 5902222810 |
| 24 | 17105674632 |
| 25 | 49612191480 |
| 26 | 143990912750 |
| 27 | 418177092554 |