Number of n-node forests not determined by their spectra.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =2a(6) =4a(7) =14a(8) =38a(9) =89a(10) =234a(11) =581a(12) =1471a(13) =3560a(14) =8940a(15) =21229a(16) =52876a(17) =126393a(18) =309993