If n mod 2 = 0 then 2*Sum(floor(C(n,w)/(2*w+1)),w=0..n/2-1)+floor(C(n,n/2)/(n+1)) otherwise 2*Sum(floor(C(n,w)/(2*w+1)),w=0..(n-1)/2).

A085570

If n mod 2 = 0 then 2*Sum(floor(C(n,w)/(2*w+1)),w=0..n/2-1)+floor(C(n,n/2)/(n+1)) otherwise 2*Sum(floor(C(n,w)/(2*w+1)),w=0..(n-1)/2).

Terms

    a(0) =1a(1) =2a(2) =2a(3) =4a(4) =5a(5) =8a(6) =14a(7) =24a(8) =39a(9) =74a(10) =128a(11) =232a(12) =423a(13) =776a(14) =1426a(15) =2660a(16) =4931a(17) =9268a(18) =17346a(19) =32840a(20) =61903a(21) =117832a(22) =223410a(23) =427156a(24) =813812a(25) =1561830a(26) =2987535a(27) =5751742a(28) =11039759a(29) =21312036

External references