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 | 2 |
| 2 | 7 |
| 3 | 21 |
| 4 | 69 |
| 5 | 183 |
| 6 | 669 |
| 7 | 1767 |
| 8 | 5721 |
| 9 | 17163 |
| 10 | 56529 |
| 11 | 149427 |
| 12 | 503721 |
| 13 | 1233963 |
| 14 | 4422609 |
| 15 | 13988547 |
| 16 | 42326001 |
| 17 | 116887923 |
| 18 | 375168249 |
| 19 | 929468907 |
| 20 | 3253991841 |
| 21 | 10227560643 |
| 22 | 31148267049 |
| 23 | 88788949947 |
| 24 | 277075307601 |
| 25 | 820517465043 |
| 26 | 2515094683929 |
| 27 | 7545284051787 |
| 28 | 22796479021761 |