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 | 4 |
| 3 | 26 |
| 4 | 188 |
| 5 | 1627 |
| 6 | 15172 |
| 7 | 154904 |
| 8 | 1670836 |
| 9 | 18951217 |
| 10 | 222682164 |
| 11 | 2693625128 |
| 12 | 33309537808 |
| 13 | 419311915217 |
| 14 | 5354144473084 |
| 15 | 69169422070152 |
| 16 | 902237854706616 |
| 17 | 11863641066687085 |
| 18 | 157052133090437332 |
| 19 | 2090929291636792824 |
| 20 | 27971914781646817864 |
| 21 | 375725009230868446500 |