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 | 3 |
| 2 | 18 |
| 3 | 124 |
| 4 | 951 |
| 5 | 7764 |
| 6 | 66200 |
| 7 | 582594 |
| 8 | 5252133 |
| 9 | 48254668 |
| 10 | 450186720 |
| 11 | 4253328540 |
| 12 | 40612877001 |
| 13 | 391300954065 |
| 14 | 3799506069816 |
| 15 | 37142836241690 |
| 16 | 365255937037437 |
| 17 | 3610755090793272 |
| 18 | 35861607622930556 |
| 19 | 357670540310182842 |
| 20 | 3580797575489620740 |