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 | 21 |
| 5 | 483 |
| 6 | 15018 |
| 7 | 258972 |
| 8 | 5554188 |
| 9 | 85421118 |
| 10 | 1558792200 |
| 11 | 22555934280 |
| 12 | 375708427812 |
| 13 | 5235847653036 |
| 14 | 82234427131416 |
| 15 | 1117259292848016 |
| 16 | 16842445235560944 |
| 17 | 224686278407291148 |
| 18 | 3286157560248860532 |
| 19 | 43241609165618454096 |
| 20 | 617910462111714896820 |