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 | 1 |
| 2 | 6 |
| 3 | 28 |
| 4 | 120 |
| 5 | 497 |
| 6 | 2016 |
| 7 | 8140 |
| 8 | 32640 |
| 9 | 130813 |
| 10 | 523776 |
| 11 | 2096133 |
| 12 | 8386580 |
| 13 | 33550335 |
| 14 | 134209524 |
| 15 | 536854528 |
| 16 | 2147450887 |
| 17 | 8589869054 |
| 18 | 34359607310 |
| 19 | 137438691321 |
| 20 | 549755289604 |
| 21 | 2199022206975 |
| 22 | 8796090925052 |
| 23 | 35184367894531 |
| 24 | 140737479966709 |
| 25 | 562949936644106 |