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 | 19 |
| 4 | 109 |
| 5 | 469 |
| 6 | 2509 |
| 7 | 12589 |
| 8 | 67399 |
| 9 | 358039 |
| 10 | 1946395 |
| 11 | 10622755 |
| 12 | 58600531 |
| 13 | 324978643 |
| 14 | 1813780243 |
| 15 | 10169519635 |
| 16 | 57273912685 |
| 17 | 323755931917 |
| 18 | 1836345339961 |
| 19 | 10446793409041 |
| 20 | 59591722204861 |
| 21 | 340755882430381 |