2nd-largest term in n-th row of Stern's diatomic triangle A002487.

Terms

a(0) =1a(1) =2a(2) =4a(3) =7a(4) =12a(5) =19a(6) =31a(7) =50a(8) =81a(9) =131a(10) =212a(11) =343a(12) =555a(13) =898a(14) =1453a(15) =2351a(16) =3804a(17) =6155a(18) =9959a(19) =16114a(20) =26073a(21) =42187a(22) =68260a(23) =110447a(24) =178707a(25) =289154a(26) =467861a(27) =757015a(28) =1224876a(29) =1981891