1085401domain: NAppears in sequencesa(n) = Sum_{k <= n/2 } binomial(n-2k, 3k+1).at n=28A137357Number of (n+1) X (1+1) arrays of permutations of 0..n*2+1 with each element having directed index change -2,0 -1,0 0,-1 or 1,1.at n=41A264622Number of compositions of 5*n-4 into parts 3 and 5.at n=17A369848