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 | 3 |
| 3 | 18 |
| 4 | 154 |
| 5 | 1632 |
| 6 | 20007 |
| 7 | 273164 |
| 8 | 4058556 |
| 9 | 64628487 |
| 10 | 1091488334 |
| 11 | 19403175105 |
| 12 | 361028420037 |
| 13 | 7000932594042 |
| 14 | 141010975529568 |
| 15 | 2942134448306481 |
| 16 | 63449975020918843 |
| 17 | 1411787024678728344 |
| 18 | 32360032648643379471 |
| 19 | 763096191377494726161 |
| 20 | 18491954778730596443088 |