Number of arrays of -4..4 integers x(1..n) with every x(i) in a subsequence of length 1 or 2 with sum zero.

A193644

Number of arrays of -4..4 integers x(1..n) with every x(i) in a subsequence of length 1 or 2 with sum zero.

Terms

    a(0) =1a(1) =9a(2) =25a(3) =105a(4) =369a(5) =1393a(6) =5105a(7) =18937a(8) =69897a(9) =258521a(10) =955361a(11) =3531745a(12) =13054177a(13) =48254185a(14) =178365177a(15) =659309641a(16) =2437064529a(17) =9008352081a(18) =33298400977a(19) =123083978969a(20) =454966715881

External references