a(n) is the number of binary strings of length n such that there exists a subsequence of length 4 containing 3 or more ones.

A118646

a(n) is the number of binary strings of length n such that there exists a subsequence of length 4 containing 3 or more ones.

Terms

    a(0) =0a(1) =0a(2) =1a(3) =5a(4) =13a(5) =31a(6) =71a(7) =159a(8) =346a(9) =739a(10) =1559a(11) =3258a(12) =6756a(13) =13922a(14) =28547a(15) =58300a(16) =118668a(17) =240880a(18) =487835a(19) =986085a(20) =1990025a(21) =4010658a(22) =8073786a(23) =16237521a(24) =32629241a(25) =65522823a(26) =131498801a(27) =263774439a(28) =528880599a(29) =1060044148

External references