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 | -1 |
| 2 | 1 |
| 3 | 11 |
| 4 | 63 |
| 5 | 499 |
| 6 | 6089 |
| 7 | 97551 |
| 8 | 1875551 |
| 9 | 41846183 |
| 10 | 1062206289 |
| 11 | 30214274419 |
| 12 | 951599063711 |
| 13 | 32864817109851 |
| 14 | 1234766859596633 |
| 15 | 50132215859126519 |
| 16 | 2187063341006059839 |
| 17 | 102022039514031274831 |
| 18 | 5067161180856909388961 |
| 19 | 266960634868753685833563 |