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) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 5 |
| 4 | 18 |
| 5 | 107 |
| 6 | 1008 |
| 7 | 13113 |
| 8 | 214238 |
| 9 | 4182487 |
| 10 | 94747196 |
| 11 | 2440784645 |
| 12 | 70431957258 |
| 13 | 2249856084803 |
| 14 | 78802876705608 |
| 15 | 3002702793753489 |
| 16 | 123649410977736950 |
| 17 | 5471808106109912815 |
| 18 | 258948617502187143188 |
| 19 | 13049542794706527317597 |
| 20 | 697673361673877090147490 |