A120181 a(1)=4; a(n)=floor((27+sum(a(1) to a(n-1)))/6).

4, 5, 6, 7, 8, 9, 11, 12, 14, 17, 20, 23, 27, 31, 36, 42, 49, 58, 67, 78, 91, 107, 124, 145, 169, 197, 230, 269, 313, 366, 427, 498, 581, 678, 791, 922, 1076, 1255, 1465, 1709