A120180 a(1)=3; a(n)=floor((20+sum(a(1) to a(n-1)))/6).

3, 3, 4, 5, 5, 6, 7, 8, 10, 11, 13, 15, 18, 21, 24, 28, 33, 39, 45, 53, 61, 72, 84, 98, 114, 133, 155, 181, 211, 246, 287, 335, 391, 456, 532, 621, 724, 845, 986, 1150