A151586 Number of permutations of 2 indistinguishable copies of 1..n arranged in a circle with exactly 5 adjacent element pairs in decreasing order.
0, 184, 41450, 2698344, 101727276, 2846840080, 66502921806, 1382518990400
Offset: 3
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.