The first, 26, terms of the sequence Sum(a(n,k)^2,k=0...infinity) where a(n,\ k) is the coefficient of Prod(1+x^(2^i+(-1)^i)+x^(2^(i+1)+(-1)^(i+1),i=0..n-1) are [1, 3, 11, 45, 197, 863, 3841, 17077, 76337, 341509, 1531543, 6875493, 30907245 , 139056207, 626170877, 2821513905, 12721321649, 57385011073, 258973449155, 1169162212701, 5280031906267, 23851817573737, 107774016006369, 487080358636849, 2201758109153721, 9954306718655255] This took, 195.158, second.