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

A193695

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

Terms

    a(0) =1a(1) =3a(2) =9a(3) =23a(4) =57a(5) =141a(6) =351a(7) =875a(8) =2181a(9) =5435a(10) =13543a(11) =33747a(12) =84093a(13) =209549a(14) =522169a(15) =1301177a(16) =3242363a(17) =8079545a(18) =20133171a(19) =50169233a(20) =125015177a(21) =311521495a(22) =776270883a(23) =1934365665a(24) =4820186623a(25) =12011275583a(26) =29930530167a(27) =74582972465a(28) =185851027385

External references