a(n) = number of integer strings s(0),...,s(n) counted by array T in A026386 that have s(n)=4; also a(n) = T(2n,n-2).

A026389

a(n) = number of integer strings s(0),...,s(n) counted by array T in A026386 that have s(n)=4; also a(n) = T(2n,n-2).

Terms

    a(0) =1a(1) =8a(2) =49a(3) =272a(4) =1440a(5) =7428a(6) =37730a(7) =189808a(8) =948909a(9) =4724160a(10) =23453001a(11) =116207424a(12) =575036475a(13) =2842936320a(14) =14046869575a(15) =69378730880a(16) =342590699955

External references