1979054

Appears in sequences

• a(n) = 2*a(n-1)+3*a(n-2)-6*a(n-3) starting a(0)=a(1)=0, a(2)=1.at n=21A167762
• a(n) = 2^n - (1 - (-1)^n)*3^((n-1)/2).at n=21A167784
• Number of subsets of {1..n} containing two distinct elements summing to n.at n=21A365544
• Number of subsets of {1..n} with two elements (possibly the same) summing to n.at n=21A366131