a(n) = (2^(n^2)+2^((n^2+n)/2))/2.A200564a(n) = (2^(n^2)+2^((n^2+n)/2))/2.Terms a(0) =1a(1) =2a(2) =12a(3) =288a(4) =33280a(5) =16793600a(6) =34360786944External referencesoeis: A200564