a(n) is the number of permutations {c_1..c_n} of {1..n} for which c_1 - c_2 + ... + (-1)^(n-1)*c_n are squares.
A293857
a(n) is the number of permutations {c_1..c_n} of {1..n} for which c_1 - c_2 + ... + (-1)^(n-1)*c_n are squares.
Terms
- a(0) =1a(1) =1a(2) =1a(3) =4a(4) =12a(5) =36a(6) =144a(7) =1440a(8) =9216a(9) =66240a(10) =504000a(11) =7344000a(12) =73612800a(13) =830995200a(14) =9373190400a(15) =181875456000
External references
- oeis: A293857