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) |
|---|---|
| 4 | 1 |
| 5 | 25 |
| 6 | 435 |
| 7 | 6545 |
| 8 | 91390 |
| 9 | 1221759 |
| 10 | 15890700 |
| 11 | 202927725 |
| 12 | 2558620845 |
| 13 | 31966749880 |
| 14 | 396704524216 |
| 15 | 4898229264825 |
| 16 | 60246643120300 |
| 17 | 738799683460650 |
| 18 | 9038619861406740 |
| 19 | 110375347398090219 |
| 20 | 1345860629046814650 |