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 | 20 |
| 3 | 169 |
| 4 | 1667 |
| 5 | 18084 |
| 6 | 208960 |
| 7 | 2527074 |
| 8 | 31630390 |
| 9 | 406680465 |
| 10 | 5342750699 |
| 11 | 71442850111 |
| 12 | 969548468960 |
| 13 | 13323571588607 |
| 14 | 185072895183632 |
| 15 | 2594890728951909 |
| 16 | 36681505784903758 |
| 17 | 522291180086851188 |
| 18 | 7484621370716999785 |
| 19 | 107876522368295972285 |
| 20 | 1562916545414144667559 |