199019520

Appears in sequences

• Number of permutations of 1..n with no adjacent pair summing to n+2.at n=12A173842
• Number of permutations of 1..n with no adjacent pair summing to n+3.at n=12A173843
• Number of permutations of {1,2,...,2n} , say x(1),x(2), ... , x(2n) , such that x(i) + x(i+1) is not equal to 2n-1 for all i, 1<=i<=2n-1.at n=5A181142