A026475 a(n) = least positive integer > a(n-1) and not a(i)+a(j)+a(k) for 1<=i<j<k<=n.

1, 3, 4, 5, 6, 7, 19, 20, 21, 22, 36, 37, 38, 39, 53, 54, 55, 69, 70, 71, 72, 86, 87, 88, 102, 103, 104, 105, 119, 120, 121, 135, 136, 137, 138, 152, 153, 154, 168, 169, 170, 171, 185, 186, 187, 201, 202, 203, 204, 218, 219, 220, 234, 235, 236, 237, 251, 252, 253