Number of arrays of -1..1 integers x(1..n) with every x(i) in a subsequence of length 1, 2, 3 or 4 with sum zero.

A193703

Number of arrays of -1..1 integers x(1..n) with every x(i) in a subsequence of length 1, 2, 3 or 4 with sum zero.

Terms

    a(0) =1a(1) =3a(2) =9a(3) =27a(4) =73a(5) =195a(6) =515a(7) =1357a(8) =3585a(9) =9479a(10) =25069a(11) =66307a(12) =175381a(13) =463859a(14) =1226827a(15) =3244745a(16) =8581777a(17) =22697291a(18) =60030393a(19) =158769987a(20) =419919089a(21) =1110613203a(22) =2937379387a(23) =7768859149a(24) =20547285345a(25) =54344006943a(26) =143730475357a(27) =380142185163

External references