a(n) = T(n, n-2), where T is given by A026519. Also number of integer strings s(0), ..., s(n), counted by T, such that s(n) = 2.

A026522

a(n) = T(n, n-2), where T is given by A026519. Also number of integer strings s(0), ..., s(n), counted by T, such that s(n) = 2.

Terms

    a(0) =1a(1) =2a(2) =5a(3) =13a(4) =27a(5) =76a(6) =150a(7) =434a(8) =845a(9) =2470a(10) =4797a(11) =14085a(12) =27377a(13) =80584a(14) =156900a(15) =462620a(16) =902394a(17) =2664276a(18) =5205950a(19) =15387670a(20) =30114073a(21) =89097932a(22) =174609162a(23) =517058502a(24) =1014555607a(25) =3006637946a(26) =5906040623a(27) =17514547015a(28) =34438443075

External references