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) |
|---|---|
| 2 | 0 |
| 3 | 0 |
| 4 | 6 |
| 5 | 66 |
| 6 | 402 |
| 7 | 2028 |
| 8 | 8790 |
| 9 | 35118 |
| 10 | 131982 |
| 11 | 475344 |
| 12 | 1658382 |
| 13 | 5651226 |
| 14 | 18912498 |
| 15 | 62418180 |
| 16 | 203768862 |
| 17 | 659487678 |
| 18 | 2119617474 |
| 19 | 6774043254 |
| 20 | 21547968726 |
| 21 | 68274910026 |
| 22 | 215609878962 |
| 23 | 678936947940 |
| 24 | 2132568719358 |
| 25 | 6683705385078 |
| 26 | 20906259913566 |
| 27 | 65277851607840 |