20030009

Appears in sequences

• Number of nonempty subsets of {1,2,...,n} in which exactly 1/2 of the elements are <= (n+1)/3.at n=28A048038
• Number of nonempty subsets of {1,2,...,n} in which exactly 1/2 of the elements are <= (n+2)/3.at n=28A048071
• Number of nonempty subsets of {1,2,...,n} in which exactly 1/2 of the elements are <= (n+3)/3.at n=28A048082
• a(n) = number of nonempty subsets S of {1,2,...,n} such that (number of nonprimes in S) = (number of primes in S).at n=29A369854