a(n) is the number of subsequences of [ 1, ..., 2n ] in which each odd number has an even neighbor.

A007482

a(n) is the number of subsequences of [ 1, ..., 2n ] in which each odd number has an even neighbor.

Terms

    a(0) =1a(1) =3a(2) =11a(3) =39a(4) =139a(5) =495a(6) =1763a(7) =6279a(8) =22363a(9) =79647a(10) =283667a(11) =1010295a(12) =3598219a(13) =12815247a(14) =45642179a(15) =162557031a(16) =578955451a(17) =2061980415a(18) =7343852147a(19) =26155517271a(20) =93154256107a(21) =331773802863

External references