90772

Appears in sequences

• Given a set of positive integers A={1,2,...,n-1,n}, n>=2. Take subsets of A of the form {1,...,n} so only subsets containing numbers 1 and n are allowed. Then a(1)=1 and a(n) is the number of subsets where arithmetic mean of the subset is an integer.at n=21A147980
• a(n) = 9*n^3/2 - 21*n^2/2 + 8*n - 4.at n=26A232495