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

A193641

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

Terms

    a(0) =1a(1) =3a(2) =7a(3) =15a(4) =33a(5) =73a(6) =161a(7) =355a(8) =783a(9) =1727a(10) =3809a(11) =8401a(12) =18529a(13) =40867a(14) =90135a(15) =198799a(16) =438465a(17) =967065a(18) =2132929a(19) =4704323a(20) =10375711a(21) =22884351a(22) =50473025a(23) =111321761a(24) =245527873a(25) =541528771a(26) =1194379303a(27) =2634286479a(28) =5810101729a(29) =12814582761

External references