Number of arrays of -3..3 integers x(1..n) with every x(i) in a subsequence of length 1 or 2 with sum zero.

A193643

Number of arrays of -3..3 integers x(1..n) with every x(i) in a subsequence of length 1 or 2 with sum zero.

Terms

    a(0) =1a(1) =7a(2) =19a(3) =67a(4) =217a(5) =721a(6) =2377a(7) =7855a(8) =25939a(9) =85675a(10) =282961a(11) =934561a(12) =3086641a(13) =10194487a(14) =33670099a(15) =111204787a(16) =367284457a(17) =1213058161a(18) =4006458937a(19) =13232434975a(20) =43703763859a(21) =144343726555a(22) =476734943521

External references