21275014800domain: NAppears in sequencesNumber of distinct perforation patterns for deriving (v,b) = (n+2,n) punctured convolutional codes from (2,1).at n=19A007223a(n) = Sum_{k=0..floor((n-1)/2)} T(n,k) * T(n,k+1), with T given by A008315.at n=19A027302Expansion of (A(x)^2 - A(x^2))/2 where A(x) = A000108(x) - 1.at n=21A275206