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 | 3 |
| 2 | 7 |
| 3 | 21 |
| 4 | 78 |
| 5 | 390 |
| 6 | 2461 |
| 7 | 17491 |
| 8 | 135226 |
| 9 | 1103076 |
| 10 | 9371892 |
| 11 | 82205622 |
| 12 | 740254762 |
| 13 | 6814312822 |
| 14 | 63920746639 |
| 15 | 609452784251 |
| 16 | 5894288690288 |
| 17 | 57728196873452 |
| 18 | 571747727911362 |
| 19 | 5719672404523644 |
| 20 | 57737110684330278 |
| 21 | 587604181217075742 |