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 | 23 |
| 4 | 175 |
| 5 | 1650 |
| 6 | 18451 |
| 7 | 237703 |
| 8 | 3457763 |
| 9 | 55967155 |
| 10 | 996755108 |
| 11 | 19360232181 |
| 12 | 407152004331 |
| 13 | 9215091412811 |
| 14 | 223307281633261 |
| 15 | 5768104533416742 |
| 16 | 158197552561322216 |
| 17 | 4591028199312877166 |
| 18 | 140551293414196198297 |