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 | 4 |
| 3 | 400 |
| 4 | 40000 |
| 5 | 2244004 |
| 6 | 4000000 |
| 7 | 42224004 |
| 8 | 224400400 |
| 9 | 400000000 |
| 10 | 424442404 |
| 11 | 4222400400 |
| 12 | 22200404004 |
| 13 | 22440040000 |
| 14 | 40000000000 |
| 15 | 42444240400 |
| 16 | 422240040000 |
| 17 | 2220040400400 |
| 18 | 2244004000000 |
| 19 | 4000000000000 |
| 20 | 4024044024004 |
| 21 | 4244424040000 |
| 22 | 40244204444224 |
| 23 | 42224004000000 |