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 | 15 |
| 2 | 153 |
| 3 | 1431 |
| 4 | 13041 |
| 5 | 117855 |
| 6 | 1062153 |
| 7 | 9563751 |
| 8 | 86086881 |
| 9 | 774821295 |
| 10 | 6973509753 |
| 11 | 62761942071 |
| 12 | 564858541521 |
| 13 | 5083730062335 |
| 14 | 45753580126953 |
| 15 | 411782249840391 |
| 16 | 3706040334656961 |
| 17 | 33354363270192975 |
| 18 | 300189270206577753 |
| 19 | 2701703434183722711 |
| 20 | 24315330914627073201 |