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 | 18 |
| 3 | 141 |
| 4 | 1380 |
| 5 | 16095 |
| 6 | 217458 |
| 7 | 3335745 |
| 8 | 57225528 |
| 9 | 1085066523 |
| 10 | 22526087070 |
| 11 | 508042140573 |
| 12 | 12367076890644 |
| 13 | 323130848000727 |
| 14 | 9018976230237834 |
| 15 | 267789942962863065 |
| 16 | 8427492557547704688 |
| 17 | 280194087519310655667 |
| 18 | 9813332205452943323190 |
| 19 | 361109786425470021564021 |