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 | 3 |
| 3 | 13 |
| 4 | 73 |
| 5 | 501 |
| 6 | 4051 |
| 7 | 37633 |
| 8 | 394353 |
| 9 | 4233673 |
| 10 | 51683491 |
| 11 | 684364341 |
| 12 | 9755819833 |
| 13 | 148749428413 |
| 14 | 2411870539443 |
| 15 | 41369113878121 |
| 16 | 746931540551521 |
| 17 | 14128241450715153 |
| 18 | 281805883597349443 |
| 19 | 5880463849670410333 |
| 20 | 128050607992266620841 |
| 21 | 2903233047048502113541 |