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 | 1 |
| 2 | 7 |
| 3 | 56 |
| 4 | 477 |
| 5 | 4180 |
| 6 | 37401 |
| 7 | 339184 |
| 8 | 3107583 |
| 9 | 28691938 |
| 10 | 266537777 |
| 11 | 2488340790 |
| 12 | 23326071990 |
| 13 | 219416722056 |
| 14 | 2070014554612 |
| 15 | 19578402111888 |
| 16 | 185583671757949 |
| 17 | 1762564846962972 |
| 18 | 16768616366059543 |
| 19 | 159777503753057786 |
| 20 | 1524516616304476102 |
| 21 | 14564266581096857240 |