Number of ternary strings of length n that contain at least two 0's and at most one 1.

Terms

a(0) =0a(1) =0a(2) =1a(3) =7a(4) =27a(5) =81a(6) =213a(7) =519a(8) =1207a(9) =2725a(10) =6033a(11) =13179a(12) =28515a(13) =61257a(14) =130861a(15) =278287a(16) =589551a(17) =1244877a(18) =2621097a(19) =5504643a(20) =11533915a(21) =24116785a(22) =50331141a(23) =104857047a(24) =218103207a(25) =452984181a(26) =939523393a(27) =1946156299a(28) =4026531027a(29) =8321498265