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) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 21 |
| 3 | 124 |
| 4 | 761 |
| 5 | 4724 |
| 6 | 29421 |
| 7 | 183404 |
| 8 | 1143601 |
| 9 | 7131364 |
| 10 | 44471301 |
| 11 | 277325404 |
| 12 | 1729418921 |
| 13 | 10784771924 |
| 14 | 67254567261 |
| 15 | 419404046924 |
| 16 | 2615432135521 |
| 17 | 16310012568004 |
| 18 | 101710347053301 |
| 19 | 634272638178364 |
| 20 | 3955367287840601 |