a(n) = T(n, n-2), T given by A026552. Also a(n) = number of integer strings s(0), ..., s(n) counted by T, such that s(n) = 2.

A026555

a(n) = T(n, n-2), T given by A026552. Also a(n) = number of integer strings s(0), ..., s(n) counted by T, such that s(n) = 2.

Terms

    a(0) =1a(1) =2a(2) =7a(3) =13a(4) =40a(5) =76a(6) =226a(7) =434a(8) =1279a(9) =2470a(10) =7267a(11) =14085a(12) =41462a(13) =80584a(14) =237484a(15) =462620a(16) =1365014a(17) =2664276a(18) =7870226a(19) =15387670a(20) =45501743a(21) =89097932a(22) =263707094a(23) =517058502a(24) =1531614109a(25) =3006637946a(26) =8912678569a(27) =17514547015a(28) =51952990090

External references