The number of necklaces with n beads of white and red colors, including at least three white ones.

Terms

a(0) =1a(1) =2a(2) =4a(3) =8a(4) =13a(5) =24a(6) =40a(7) =71a(8) =119a(9) =216a(10) =372a(11) =678a(12) =1215a(13) =2240a(14) =4102a(15) =7674a(16) =14299a(17) =27000a(18) =50952a(19) =96896a(20) =184397a(21) =352684a(22) =675174a(23) =1296843a(24) =2493711a(25) =4806062a(26) =9272764a(27) =17920843a(28) =34669585a(29) =67159032