Number of irredundant sets in the (2n-1)-triangular snake graph (for n > 1).

Terms

a(0) =1a(1) =4a(2) =10a(3) =25a(4) =64a(5) =163a(6) =415a(7) =1057a(8) =2692a(9) =6856a(10) =17461a(11) =44470a(12) =113257a(13) =288445a(14) =734617a(15) =1870936a(16) =4764934a(17) =12135421a(18) =30906712a(19) =78713779a(20) =200469691a(21) =510559873a(22) =1300303216a(23) =3311635996a(24) =8434135081a(25) =21480209374a(26) =54706189825a(27) =139326724105a(28) =354839847409a(29) =903712608748