Number of permutations p of (1,2,3,...,n) such that Sum_{k=1..n} gcd(k,p(k)) = sigma(n).

A073343

Number of permutations p of (1,2,3,...,n) such that Sum_{k=1..n} gcd(k,p(k)) = sigma(n).

Terms

    a(0) =1a(1) =1a(2) =1a(3) =6a(4) =33a(5) =75a(6) =877a(7) =2075a(8) =38692a(9) =239794a(10) =1250340a(11) =18495201a(12) =43023264a(13) =4554211553a(14) =70490483945a(15) =911526001064a(16) =182477118528

External references