Imaginary parts of terms (1,1), (2,2) of matrix [1,(1+I); 1,1]^n.

Terms

a(0) =0a(1) =1a(2) =3a(3) =8a(4) =20a(5) =47a(6) =105a(7) =224a(8) =456a(9) =881a(10) =1595a(11) =2632a(12) =3692a(13) =3359a(14) =-2927a(15) =-27776a(16) =-103088a(17) =-304607a(18) =-803149a(19) =-1966392a(20) =-4549884a(21) =-10029361a(22) =-21114759a(23) =-42375200a(24) =-80491880a(25) =-142437359a(26) =-226667157a(27) =-294543992a(28) =-191015460a(29) =556551487