Number of permutations p from (1,2,3,...,n) to (1,2,3...,n) such that 1/p(1)+2/p(2)+...+n/p(n) is an integer.
A073090
Number of permutations p from (1,2,3,...,n) to (1,2,3...,n) such that 1/p(1)+2/p(2)+...+n/p(n) is an integer.
Terms
- a(0) =1a(1) =1a(2) =1a(3) =1a(4) =2a(5) =2a(6) =8a(7) =8a(8) =22a(9) =104a(10) =1128a(11) =1128a(12) =14520a(13) =14520a(14) =229734a(15) =3217088a(16) =21157428a(17) =21157428
External references
- oeis: A073090