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 | 0 |
| 3 | 1 |
| 4 | 4 |
| 5 | 14 |
| 6 | 65 |
| 7 | 572 |
| 8 | 7434 |
| 9 | 163284 |
| 10 | 5736792 |
| 11 | 342169618 |
| 12 | 33534958026 |
| 13 | 5442700283638 |
| 14 | 1484664947481018 |
| 15 | 664513607618098252 |
| 16 | 508538464299684269212 |
| 17 | 635542752091150346032474 |
| 18 | 1374528064543284187245552390 |
| 19 | 4842758246111267151697826493193 |
| 20 | 29772724415959420224886585241636839 |