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 | 0 |
| 1 | 0 |
| 2 | 2 |
| 3 | 13 |
| 4 | 128 |
| 5 | 1562 |
| 6 | 23328 |
| 7 | 411771 |
| 8 | 8388608 |
| 9 | 193710244 |
| 10 | 5000000000 |
| 11 | 142655835305 |
| 12 | 4458050224128 |
| 13 | 151437553296126 |
| 14 | 5556003412779008 |
| 15 | 218946945190429687 |
| 16 | 9223372036854775808 |
| 17 | 413620130943168382088 |
| 18 | 19673204037648268787712 |
| 19 | 989209827830156794561989 |