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 | 0 |
| 2 | 1 |
| 3 | 5 |
| 4 | 33 |
| 5 | 257 |
| 6 | 2443 |
| 7 | 27682 |
| 8 | 363759 |
| 9 | 5405697 |
| 10 | 89134360 |
| 11 | 1609418390 |
| 12 | 31525697245 |
| 13 | 665263778962 |
| 14 | 15039817276939 |
| 15 | 362579178545598 |
| 16 | 9284375250749758 |
| 17 | 251643492565059981 |
| 18 | 7197256536139662143 |
| 19 | 216621907269166632361 |
| 20 | 6844093745422473471562 |