Coefficient of x^2 in (1+x)^n mod 1+x^4.

Terms

a(0) =0a(1) =0a(2) =1a(3) =3a(4) =6a(5) =10a(6) =14a(7) =14a(8) =0a(9) =-48a(10) =-164a(11) =-396a(12) =-792a(13) =-1352a(14) =-1912a(15) =-1912a(16) =0a(17) =6528a(18) =22288a(19) =53808a(20) =107616a(21) =183712a(22) =259808a(23) =259808a(24) =0a(25) =-887040a(26) =-3028544a(27) =-7311552a(28) =-14623104a(29) =-24963200