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 | 4 |
| 1 | 17 |
| 2 | 87 |
| 3 | 503 |
| 4 | 3123 |
| 5 | 20207 |
| 6 | 134067 |
| 7 | 903983 |
| 8 | 6162243 |
| 9 | 42326927 |
| 10 | 292300947 |
| 11 | 2026334063 |
| 12 | 14085963363 |
| 13 | 98111316047 |
| 14 | 684331387827 |
| 15 | 4778093469743 |
| 16 | 33385561572483 |
| 17 | 233393582711567 |
| 18 | 1632228682858707 |
| 19 | 11417969834487023 |
| 20 | 79887637217085603 |
| 21 | 559022711703937487 |