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 | 30 |
| 3 | 203 |
| 4 | 1394 |
| 5 | 9552 |
| 6 | 65473 |
| 7 | 448756 |
| 8 | 3075822 |
| 9 | 21081995 |
| 10 | 144498146 |
| 11 | 990405024 |
| 12 | 6788337025 |
| 13 | 46527954148 |
| 14 | 318907342014 |
| 15 | 2185823439947 |
| 16 | 14981856737618 |
| 17 | 102687173723376 |
| 18 | 703828359326017 |
| 19 | 4824111341558740 |
| 20 | 33064951031585166 |
| 21 | 226630545879537419 |